I remember a company, polarrose.com, who offered a face search engine. After a while they where asking you for your Facebook credentials (would you please give me your FB ID and passwd, sir?), crawl your account for tagged faces to extend their database. Googling shows they got bought from Apple a while ago [http://news.cnet.com/8301-13579_3-20017018-37.html] and the guy [http://www.maths.lth.se/~solem] moved to SF. There is also http://whozat.com , which searches social networks for names; I am pretty sure that at given moment they where doing face recognition.