You're not going to quit Facebook, and that's ok. But still, you should know the definitive reason why would you should quit it: This 4-minute video gives a lot of strong arguments against it, but the best is the "Imagine Facebook Is Your Best Friend Argument."
"Then one day you go to your friend's house and, by chance, you discover that he has been storing your private conversations, your photos, your videos, and basically every bit of personal info you share with him. Everything. Would you be creeped out? Then imagine that, on top of that, you discover that he has been sharing it with others behind your back.
Would you, in all honesty, still be friends with this "friend"?"
The problem with this premise is that we knew from the beginning that Facebook was storing everything we were giving them. We were giving them that information with the intent of sharing it with other people. Could Facebook be better about privacy? Sure. But you can't blame Facebook for sharing information with people that you told it you wanted to share information with. Facebook is a website for sharing information; we volunteer any information it gets from us. There's nothing sneaky about that.
Or am I missing something?