"To search for information, a user sends a question to his own referral agent, which broadcasts the query to all of the user's buddies' agents, said Zhang [researcher at University of Michigan]. A referral agent in the buddy's messenger searches its information identity profile to see if that person is likely to be able to answer the question. If not, the agent either returns empty results or forwards the query to its buddies, depending on how the user has set the software. When a likely match is found, that person sees the question and the path the query traveled, said Zhang. This friend-of-a-friend or friend-of-a-friend-of-a-friend of the questioner "can either start chatting immediately, or discuss the questions... later if the answering person prefers not to be disturbed at that time," he said."
More at TRN.