I don't think de-friending your boss would stop him from spying on you if he wanted.. If you really wanted that, I guess you should de-friend everyone you know, who knows someone, who knows your boss.
I'm still not getting this social networking thing though. 5 years ago I was considered a freak for hanging around forums and icq, today I'm lame for not having a facebook or myspace account. What has happened during these 5 years? But I have a flickr account, a gravatar, an openid, ... and again that's considered geeky. Should I just wait a few years?