Announcing new users of an electronic communications system to existing users

1. A computer-implemented method for populating participant lists for users of an electronic communications system, the method comprising:

accessing, from a memory device, information from one or more contact lists associated with a first user of an electronic communications system;

identifying a second user of the electronic communications system known to the first user based on the accessed information from the one or more contact lists associated with the first user, wherein the second user is one of a plurality of contacts identified within the one or more contact lists associated with the first user;

comparing the identified second user to data maintained on behalf of the electronic communications system, the data including information about one or more previously registered users of the electronic communications system;

determining whether the identified second user is one of the previously registered users of the electronic communications system based on the comparison of the identified second user to the data, wherein the second user is identified with an identifier;

calculating a communications strength between the first user and the identified second user, wherein the communications strength is a numerical measure representing the strength of the relationship between the first user and the identified second user with respect to at least one of:

exchanging electronic messages between the first user and the identified second user,

the amount of contact information between the first user and identified second user,

the degree of separation between the first user and identified second user,

characteristics shared between the first user and the identified second user, or

a relationship between the first user and a third user, the third user having a separate relationship with the identified second user; and

adding the identifier for the identified second user to a participant list associated with the first user in the electronic communications system, based on the determined communications strength and a maximum capacity of the participant list wherein:

the electronic communications system is one or more of an instant message system, an e-mail system, and a chat system; and

the one or more contact lists include one or more of a buddy list of an instant messaging system, an e-mail address book of an e-mail system, an e-mail distribution list, a list of people in the first user's social network, a list of people in a phone book of a mobile telephone used by the first user, a list of members of an organization that includes the first user, and a white list of people from whom communications are allowed.

2. The method of claim 1 , wherein the second user is one of a plurality of contacts identified within the one or more contact lists associated with the first user, and the method further comprises:

determining whether or not each of the plurality of contacts from the one or more contact lists is another user of the electronic communications system based on the information accessed from the one or more contact lists associated with each contact, wherein other users of the electronic communications system are identified by an identifier corresponding to each of the other users within the electronic communications system; and

upon determining that at least one of the plurality of contacts from the one or more contact lists is another user of the electronic communications system, identifying an identifier for the contact within the electronic communications system, wherein the identifier identified for the contact is added to the participant list associated with the first user.

3. The method of claim 2 , wherein the adding step comprises:

selecting contacts from the one or more contact lists that are identified as being other users of the electronic communications system to be added to the participant list associated with the first user, based on respective communications strengths between the first user and each of the selected contacts; and

adding identifiers identified for the selected contacts to the participant list associated with the first user within the electronic communications system.

4. The method of claim 3 , wherein the determined communications strength for each of the selected contacts is above a threshold value that is indicative of a relatively high communications strength between that selected contact and the first user.

5. The method of claim 3 , wherein the selecting step comprises:

sorting a list of the contacts identified as being other users of the electronic communications system, based on the respective communications strengths between the first user and the contacts in the list;

determining a maximum capacity of the participant list; and

selecting a number of the contacts from the sorted list to be added to the participant list associated with the first user, the selected number of contacts being less than or equal to the determined maximum capacity of the participant list.

6. The method of claim 2 , further comprising:

upon determining that at least one of the plurality of contacts from the one or more contact lists is not another user of the electronic communications system, sending, to the contact via a communication network, an invitation to join the electronic communications system, based on the information accessed for that contact from the one or more contact lists.

7. The method of claim 1 , wherein the communications strength is calculated based on a relationship between the first user and the second user.

8. The method of claim 7 , wherein the communications strength is calculated based on a numerical measure of one or more characteristics shared between the first and second users, the numerical measure representing a strength of the relationship between the first user and the second user.

9. The method of claim 1 , wherein calculating communications strength between the first user and the second user comprises:

calculating a communications strength between the first user and a third user based on a relationship between the first and third users, the third user also having a separate relationship with the second user;

calculating a communications strength between the second user and the third user based on the relationship between the second and third users;

determining an expected relationship between the first and second users based on the calculated communications strengths between the third user and the respective first and second users; and

calculating the communications strength between the first user and the second user based on the expected relationship determined for the first and second users.

10. The method of claim 1 , wherein users added to the participant list associated with the first user are categorized into one or more groups, and the method further comprises:

determining whether or not the second user belongs in any of the one or more groups existing currently in the participant list; and

upon determining that the second user does not belong to any of the one or more existing groups in the participant list, creating a new group within the participant list for the second user.

11. A system for populating participant lists for users of an electronic communications system, the system comprising:

a processor;

a memory including processor-readable instructions, which when executed by the processor, configure the processor to perform a plurality of functions, including functions to:

access information from one or more contact lists associated with a first user of an electronic communications system;

identify a second user of the electronic communications system known to the first user based on the accessed information from the one or more contact lists associated with the first user, wherein the second user is one of a plurality of contacts identified within the one or more contact lists associated with the first user;

compare the identified second user to data maintained on behalf of the electronic communications system, the data including information about one or more previously registered users of the electronic communications system;

determine whether the identified second user is one of the previously registered users of the electronic communications system based on the comparison of the identified second user to the data, wherein the second user is identified with an identifier;

calculate a communications strength between the first user and the identified second user, wherein the communications strength is a numerical measure representing the strength of the relationship between the first user and the identified second user with respect to at least one of:

exchanging electronic messages between the first user and the identified second user,

the amount of contact information between the first user and identified second user,

the degree of separation between the first user and identified second user,

characteristics shared between the first user and the identified second user, or

a relationship between the first user and a third user, the third user having a separate relationship with the identified second user; and

add the identifier for the identified second user to a participant list associated with the first user in the electronic communications system, based on the determined communications strength and a maximum capacity of the participant list, wherein:

the electronic communications system is one or more of an instant message system, an e-mail system, and a chat system; and

the one or more contact lists include one or more of a buddy list of an instant messaging system, an e-mail address book of an e-mail system, an e-mail distribution list, a list of people in the first user's social network, a list of people in a phone book of a mobile telephone used by the first user, a list of members of an organization that includes the first user, and a white list of people from whom communications are allowed.

12. The system of claim 11 , wherein users added to the participant list associated with the first user are categorized into one or more groups, and the processor is further configured to perform functions to:

determine whether or not the second user belongs in any of the one or more groups existing currently in the participant list; and

create a new group within the participant list for the second user when it is determined that the second user does not belong to any of the one or more existing groups in the participant list.

13. The system of claim 12 , wherein the processor is configured to:

select contacts from the one or more contact lists that are identified as being other users of the electronic communications system to be added to the participant list associated with the first user, based on respective communications strengths between the first user and each of the selected contacts; and add identifiers identified for the selected contacts to the participant list associated with the first user within the electronic communications system.

14. The system of claim 13 , wherein the communications strength determined for each of the selected contacts is above a threshold value indicating a relatively high communications strength between that selected contact and the first user.

15. The system of claim 12 , wherein the processor is further configured to:

send, to at least one of the plurality of contacts from the one or more contact lists that is determined not to be another user of the electronic communications system, an invitation to join the electronic communications system, based on the information accessed for that contact from the one or more contact lists.

16. The system of claim 11 , wherein the communications strength is calculated based on a numerical measure representing one or more characteristics of a relationship between the first user and the second user.

17. The system of claim 11 , wherein the processor is configured to perform functions to:

calculate a communications strength between the first user and a third user based on a relationship between the first and third users, the third user also having a separate relationship with the second user;

calculate a communications strength between the second user and the third user based on the relationship between the second and third users;

determine an expected relationship between the first and second users based on the calculated communications strengths between the third user and the respective first and second users; and

calculate the communications strength between the first user and the second user based on the expected relationship determined for the first and second users.

18. The system of claim 11 , wherein the second user is one of a plurality of contacts identified within the one or more contact lists associated with the first user, and the processor is further configured to perform functions to:

determine whether or not each of the plurality of contacts from the one or more contact lists is another user of the electronic communications system based on the information accessed from the one or more contact lists associated with each contact, wherein other users of the electronic communications systems are identified by an identifier corresponding to each of the other users within the electronic communications system; and

identify an identifier for at least one of the plurality of contacts determined to be another user of the electronic communications system, wherein the identifier identified for the contact is added to the participant list associated with the first user.

19. A non-transitory computer-readable medium storing instructions that, when executed by a computer, cause the computer to perform functions to:

access information from one or more contact lists associated with a first user of an electronic communications system;

identify a second user of the electronic communications system known to the first user based on the accessed information from the one or more contact lists associated with the first user, wherein the second user is one of a plurality of contacts identified within the one or more contact lists associated with the first user;

compare the identified second user to data maintained on behalf of the electronic communications system, the data including information about one or more previously registered users of the electronic communications system;

determine whether the identified second user is one of the previously registered users of the electronic communications system based on the comparison of the identified second user to the data, wherein the second user is identified with an identifier;

calculate a communications strength between the first user and the identified second user, wherein the communications strength is a numerical measure representing the strength of the relationship between the first user and the identified second user with respect to at least one of:

exchanging electronic messages between the first user and the identified second user,

the amount of contact information between the first user and identified second user,

the degree of separation between the first user and identified second user,

characteristics shared between the first user and the identified second user, or

a relationship between the first user and a third user, the third user having a separate relationship with the identified second user; and

add the identifier for the identified second user to a participant list associated with the first user in the electronic communications system, based on the determined communications strength and a maximum capacity of the participant list wherein:

the electronic communications system is one or more of an instant message system, an e-mail system, and a chat system; and

the one or more contact lists include one or more of a buddy list of an instant messaging system, an e-mail address book of an e-mail system, an e-mail distribution list, a list of people in the first user's social network, a list of people in a phone book of a mobile telephone used by the first user, a list of members of an organization that includes the first user, and a white list of people from whom communications are allowed.