Agreed it's a huge risk, but FB users have been getting shafted for ages in terms of privacy, and have hardly blinked. Geeks and privacy-oriented people yes, but most just want to share pics, see what their friends are doing and play games. It's easier to tweak their privacy settings than move to a place where they can't as easily (or automatically) share pics, have to build up their friend network from scratch, and there aren't as many games.