Okay, many of you have heard my MySpace horror story (fake page for me made by some students in another state...long story...)
However, as a adjunct professor this term, I had the ability to create a Facebook account. It is much easier to use, the interface is a million times better, and it there are many customizable options for allowing and dis-allowing access to parts of your own account. For instance, you can allow people who want to be your friends access to only your "demographic" data, while limiting access to your friends list, photos, and wall postings. It is easy to keep a small group of friends "in the know" without letting the whole universe know everything about you.
Since there is now a Facebook for high school students, I suggest working in some education on how to keep yourself "safe" at that level, too, using Facebook as the demo site. (We currently have MySpace education built into the middle school curriculum.)