Have you been watching The Virtual Revolution, with the ace Dr Aleks Krotoski.
Saturdays was very interesting, a journo traced one individual user based on so called anonymous search queries that were released for public viewing. I consider myself reasonably savvy with the net, but this program opened my eyes a bit. I do feel that people throw away their privacy, thinking it's just the net, or it's just cctv, or it's just Farmville, with little thought to future implications. To sign up to these facebook apps, you are giving access to your data to the company that runs the 3rd party app.
As for Facebook itself, why confine yourself and anything you do want to express about yourself to the defined limits of FB, the program talks about this and suggests that the web is not as rich and individual as it used to be.