1. A method of identifying a social network member as potentially possessing information about a topic so the social network member can be returned by a search conducted in an attempt to locate the information, the method comprising the steps of: storing historical data generated by the network member's exposure or communications with databases; establishing that the network member has previously been exposed to a database likely to possess useful information about the topic; and attributing an initial likelihood that the network member possesses the useful information based at least in part on the network member's previous exposure to the database.