I don't think there is anything socially redeeming about facebook or myspace. I find that people are very naive when they think anything posted is private and just for viewing by "friends". You can not believe how many people have lost jobs, scholarships, etc. over these sort of accounts. They are as public as any internet forum in many ways.
We should always remember the old rule: "Once something is posted anywhere it will be there forever." I was amazed to find an old lecture of mine (posted on a school server in 2000 which has now been eliminated but required a password to get into) still circulating on the internet. I didn't post it for any use other than my own classroom but the fact that it was in the top 2 "hits" under that topic says a lot. I wonder what would have happened if I actually intended to post it for the world's use?
Maybe I ought to think a lot more about writing more curriculum again. It would eat into my fun time however.