Another of these very obvious ideas that nobody has thought of implementing before: Bonsoir by R. Tyler Ballance at Bleepsoft:
“Bonsoir takes advantage of Cocoa Distributed Objects, Bonjour, and the Address Book API for allowing the quick and easy sharing of vCards on a local network. The basic idea was that everybody could grab Bonsoir here at BarCampTexas, select their vCards, and we could all add each other (into Address Book) to help keep in touch for the next BarCamp, etc.”
I think it nicely complements SubEthaEdit as a social networking tool at conferences. A tool to automatically grab profile and contact information of participants should be integral part of any collaboration application.