BuddyPress.org

With all due respect:

This would seem to me to not only be a critical aspect of any social network, but also a rather simple one to implement. Then again, I’m no coder.

Obviously this feature is coming, but it hasn’t happened yet.

For 1.2, Jeff Sayre is updating his privacy plugin http://jeffsayre.com/2009/12/05/buddypress-privacy-component-released/. That’s one solution on its way. Otherwise, you can implement a lot of “stop people seeing this” in child themes.