“Pookie: You really think the reason your friend is leaving frumkeit is because he has a facebook page?”
I agree with NY MOM. If someone is going to go OTD, or head in that direction, there is a great deal more going on with him or her than a Facebook page. It may only be that the signs become more obvious with Facebook. I do think that the privacy settings issue is an important one. Kids tend to forget that once something is in cyberspace it is there forever.