While facebook is far less open than myspace, for adults at least it is more open that some people think. Maybe you already know all this Lylah, but I thought I'd throw it out here for the other parents. It is true that if you do not have a facebook that you cannot see people's pages, but it is sometimes possible see people's pages as long as you have a facebook.
It does depend on some settings if people other than their friends can see them. If you are part of a Network then depending on your privacy settings, everyone within that network can see all, part or none of your profile - regardless of if they are your friends. This is under Privacy - Profile. Since region networks don't require any kind of authentication to see if you actually live there, I can change my region network to another city and check out other profiles. Facebook does limit the number of times a person can change their region (twice every 60 days) but with the variety of free email accounts a person can also make of plenty of fictitious accounts.
Okay, now I have to figure out how safe kids really are on Facebook, since I have way too much time on my hands and multiple email accounts. I'm fairly certain that Facebook would delete my accounts if they knew - luckily I'll take care of that myself once I'm done experimenting.
My new 'person' was born in 1994 (which would make them 13/14 and seriously how am I turning 26 this year?!?). While I can join other networks, I cannot view my teen self when logged in as my adult self. While being my teen self I cannot view anyone's profile. Until I get validated as someone going to a high school, I am cannot view the other profiles in that high school. And kids cannot change when they were born. And adults cannot change their age to less than 18. I'm not going to try it, but I think if I could get validated as a high school student I would be able to see the profiles of other high school students. I'm not going to push my luck though. I'd hate to lose the facebook account that I actually use.