If someone publishes a picture (e.g. in a newspaper or mag) they have to get signed permission from all the people in the picture.
Does this apply with Facebook? Is it actually illegal to post pictures of other people without their consent? Common sense seems to me to say it probably is.
Perhaps there could be an clause in FB that your friends are allowed to post pics of you but no-one else is without permission. I'd be surprised if there isn't a high profile case of this kind soon, if there hasn't been already.