This is the route that Diaspora and those who want to be "the next Facebook" should have taken. Just give ordinary users a mechanism for sharing things with their closest friends that's easier yet just as flexible as email, and you have a winner.

Idea: have an easy way of sharing stuff that's for "everyone except for the parents." (Also have a way of tagging friends who are your parent's closest friends.) Combine this with a way of tagging already-published stuff as "not for the parents" which will revoke items which you've already sent. (Also delay everything sent to parents and friends of parents by 30 minutes or so, so you have time to change your mind without their ever knowing.)

EDIT: We're reaching the point where your computer/smartphone photo sharing mechanism can detect your face in photos and detect scantily clad people. We should be able to have the device detect these conditions and your parents on the recipients list and pop up a dialog asking, "There's racy content in this photo, do you want your parents to see it?"