I think it's pretty dumb.
1) So, there's no way teachers can molest students any other way, like talking on the phone or even meeting in person?
2) It's none of the government's business who is whose friend on social networking sites, as long as nothing sexual or anything bad is going on.
3) Teachers aren't even allowed to friend students who have graduated. That makes it even worse.
Furthermore, I don't think it's even the school's business, as long as no online activities are happening at school and nothing sexual is happening.