I deactivate my MySpace after the site went crazy. I don't Twitter. I have FB on private and only add and keep in touch with close family and friends. I'll log into FB once a day (usually through my phone) to see what's happening.
Social network can have its bad and good side.
It's good if you want to keep in contact w/family and friends or show your hobbies, etc. It's not good in my opinion, because I have seen some friends or public FB page, where he/she expose too much info, and I just had this "safety" conversation w/a friend.
There are way too many bad people out there. You have the hackers, the predators, etc... And they are the ones who are prying on the vulnerable (the ones who shares too much info). A friend of my friend was stalked by this FB stalker because her page was public. She's gorgeous no doubt, and love to take pictures and post them up. This stalker doesn't know her but was able to get her location through her pictures. It doesn't take a genius to figure out where you live, where you hang out at, and who your friends are. I just saw a news investigation the other night where bad people can get through your FB/Twitter or other info through your phone via your GPS navigation.
Whatever you do online or share on your social network is your business, just becareful.