Systems, methods and apparatus for delivering content to an audience member over a computer network. A console allows a user to define audience segments that are organized in hierarchical fashion. The segments are then calculated by collecting profile data for audience members and determining whether members have attributes that a defined by the audience segments. The hierarchical definition of segments allows audience segments to be logically combined and facilitates efficient recalculation of audience segments. Profile synchronization provides an authoritative identifier that is used to reconcile the potential issuance of multiple identifiers for a given audience member.