Google’s Picasa web service has an excellent new person tagging and face recognition features. Some times it gets a little confused. The above example, which is particularly comical, is one of the extreme examples. Most of the bogus faces are close ups of ears. I do really like these features (when they are working). I was primarily using tags for people so this removes a lot of work.
The social enhancements have a long way to go yet. There a whole bunch of sharing cases that are not covered.