A: I'm sorry to say it, man, but...yeah.
First off, a little piece of advice that I like to give out to people is DO NOT go looking through stuff (phones, email, history, mail) unless you have reason to believe they're cheating or being sketchy. Chances are, you're going to see shit you don't wanna see or stuff you shouldn't see (like an order for a Christmas present!). It's not that they're hiding, but I think people have the right to certain private activity without being judged or gotten mad at. If it's not cheating or sketchy behavior with other people, then it's fine.
For most women, that's looking up their ex's on facebook. Yes, initially I can see why you'd be a little upset, but I assure you it's NOTHING. We women are a curious and competitive species and when we do this, we are not admiring our boyfriends or longing for them, but rather, we are COMPARING ourselves to them (and their girlfriends)! It's rather funny, really. Unless your girlfriend is a jerk and wanting someone else while she's with you, you have absolutely NOTHING to worry about. I, for instance, stalk everybody's profile. It's just amusing. I have no shame in it because Facebook makes it possible. Does it make me any less crazy about my man? Hell no :P lolllll