Lenny Foner's PhD thesis on Yenta describes a privacy-aware matchmaking system based on the contents of a user's profile. The thesis caps much of the work, some published some not, of Pattie Maes's group at the MIT Media Lab during the mid-1990s. I would argue that this group's work pre-dates and was a superset of much of the social network tools now popular. Foner's thesis provides pointers to much of this

The Circle of Friends (1999) as implemented on Llantrisant Online (2001) allows users to add friends manually and recommends 'friends' from genealogical data, increasing their reputation when they add them.

A personal profile, called CommunityNet, is established for each individual based on a novel algorithm incorporating contact, content, and time information simultaneously. It can be used for personal social capital management. Clusters of CommunityNets provide a view of informal networks for organization management. Our new algorithm is developed based on the combination of dynamic algorithms in the social network field and the semantic content classification methods in the natural language processing and machine learning literatures.