why do people worry about facebook, myspace etc. privacy?

[One]

I read something in the newspaper that really pissed me off b/c they are treating people like they don't have common sense. This person was saying be cautious of what you write on your profile b/c colleges can check them out and ofcourse employeers(but that another subject) but first of all how can they check your profile out unless they're part of your school network?even if they send you a friend request not many people accept strangers; atleast i don't. seoond of all their could be someone with the same name and same grade at your school. you can set it to private. heck on facebook you can even make yourself unsearchable. you can hide pictures of yourself, wall posts, statuses etc. even if they hack into it somehow that violates the terms of use and they must have some pretty powerful software! i seriously just think people like to worry.
how can you view your employes profile that's private?