1. A computer-implemented method for communication in a social networking system, the method comprising: receiving a content item from an author, the author being a user of a social networking system; receiving a definition of a first audience from the author, the first audience comprising one or more users of the social networking system; receiving a content item tag from the author, the content item tag indicating an association between the content item and a tagged user, wherein the tagged user is a user of the social networking system different than the author; receiving a definition of a second audience from the tagged user, the second audience comprising one or more users of the social networking system, wherein at least one user in the second audience is not in the first audience; determining if a viewing user is a member of a union of the first audience and the second audience; and sending the content item and the content item tag for display to the viewing user if the viewing user is a member of a union of the first audience and the second audience.
13. The method of claim 1 , wherein the second audience is defined as a set of users of the social networking system who have previously established a connection to the tagged user.