Playing devils advocate here, but I also kind of believe this... There is no such thing as privacy in the social network. It is foolhardy to assume it is even possible. Even a real life social network relies on trust, trust that can be broken very easily and totally outside of your control. Maybe the answer is to accept that privacy isn't a real thing and stop sharing things, even in what you assume is a protected environment, that you don't wish to be public. I don't think there is a technical solution to "people can't keep secrets"