A social network circuit includes two or more members of a social network in live communication with one another. Systems and methods of administering social network circuits include computing devices configured to determine the existence and extent of social network circuits. Client applications associated with computing devices used by each member may be configured to provide one or more servers with session data indicating the existence of live communication links. Based on the session data, the server(s) may track one or more social network circuits. Data representing the circuits may be provided to the clients in the circuits. Clients may selectively participate in social network circuits based on user- and system-provided parameters. For example, a subset of social network users in active communication may be further divided into a particular social network circuit devoted to a particular topic of discussion. Users may participate in multiple social network circuits at any given time.