You may call people like me paronoid but I really think its better to be safe than sorry. Read zis :
In a nutshell, facebook is big brother. Apparently it's funded by the CIA, they use it to keep tabs on everyone (all 500 million of you) know what you're doing, all your private info etc
Should I be wrong about social networking sites, it didn't kill me for not joining so it's a win win situation :] winning! I haz tiger blood.