1. A targeting system comprising: a targeting server comprising a processor and a memory storing a database; wherein the targeting server: obtains data from at least one server that forms part of an online social network, where the obtained data describes member profiles of members of the online social network and activities performed on the online social network that are associated with the member profiles; detects affinity data describing affinities between a member profile and one or more keywords based upon data describing activities associated with the member profile; generates a database containing the member profiles and the affinity data associating the detected affinities between member profiles and keywords; identifies member profile data describing member profiles within the database that are associated with an affinity to at least one offer keyword; identifies targeting keywords based on the at least one offer keywords and the member profile data by identifying at least one additional keyword within the at least one offer keyword based on the affinity of the member profiles within the member profile data; identifies other keywords for which the identified member profiles have an associated affinity; selects a set of keywords including at least one of the identified keywords and at least one of the targeting keywords as targeting keywords for the specific offer, where the selected keywords target the desired audience for the specific offer; generates a set of targeting keywords that target a specific offer to a desired audience based on the selected set of keywords; and provides the set of targeting keywords.
3. The targeting system of claim 1 , wherein the targeting server scores the affinity between a member profile and one or more keywords within data describing an activity associated with the member profile.