There are an awful lot of pictures of people on facebook that are "tagged", meaning it tells you who is in the picture and some even have a frame around the face of the person. This could put face recognition software to a real test. How about grabbing lots of pictures, looking at who is in them, and then sifting through other pictures trying to find out who is in them?
As there are so many pictures of the same person on facebook chances are one of them will be suited to be the one to use for trying to match that person on other pictures.
This could be a fun project at some point.
All the personal data about people on pages like facebook plus a good image of them, hello spammers I say. Or other people relying on such information
Attacks
watch this space for more intresting ideas how to make use of all these social networking sites. Some more intresting ideas and worries expressed in german on http://seclog.de/2006/09/04/studivznet-facebookorg-oder-die-drohende-gotterdammerung-des-social-networking/#more-75