20. The computer storage medium of claim 19 , which further causes the computer to perform a further operation comprising: outputting, in response to input from a user, an identity of one or more of the selected users.
19. A computer storage medium having computer executable instructions which when executed by a computer cause the computer to perform operations comprising: receiving information for a source user, the information including at least one topic and a user value for each topic, where: the user value represents how strongly the user is associated with that topic, and the user value includes a user authority value representing a user expertise related to that topic and a user interest value representing a degree of user association with that topic; generating similarity scores based on a user value for each topic for the source user and a user value for the same topic for each user in a set of users, where each user in the set of users is associated with a user value for each topic; selecting one or more similar users based on the generated similarity scores; outputting one or more of the selected users; and outputting the identity of one or more overlapping topics and a value indicating a degree of overlap for each overlapping topic.