Audience management in a social networking system

A social networking system manages the accessibility of content items provided by users and directed to various audiences in the social networking system. An author provides the social networking system with a content item, a content item tag indicating an association between the content item and a tagged user, and a definition of a first audience who may view the content item. The social networking system then allows the tagged user to provide a definition of a second audience who may view the content item, where the second audience may contains users who are not in the first audience defined by the original author. The social networking system then determines whether a viewing user may view the posted content item (and tag) based on whether the viewing user is in at least one of the first audience and the second audience.