A server receives an interaction history comprising a set of one-to-one interactions between a first user and other users. The server determines an interaction score for each of the interactions, wherein each interaction score is based on a type of the respective one-to-one interaction and an age of the respective one-to-one interaction. The server then determines a friend rank for each of the other users based on the interaction history, wherein the friend rank indicates a measure of a degree of influence the other users have over the first user and stores the friend rank for each of the other users. The server then receives, from a client, a request for an advertisement to display to the first user, selects one of the other users having a friend rank satisfying a predetermined threshold, and transmits, to the client, an advertisement portraying the selected additional user.