Well I haven't had success in getting my old girlfriends to join my "psycho exes" group, so I'm not sure how effective Facebook's system currently is ;)
Facebook's privacy settings are now pretty good. You can make things visible or invisible to everyone, networks, friends of friends, friends, friend lists or individuals and any combination of these things, e.g. a status update visible only to family except my mother.
Will it allow me to split my friends into separate lists, and then have separate news feeds for each of those lists? I can see that I am able to post a status update and specify a list when I do it, but it ends up getting mixed into my normal news feed and doesn't have any indication of who can see it. This just feels dangerous to me.
I'll start using Facebook lists when they implement it properly. I want my lists of friends to be 100% completely separate. Separate walls, separate news feeds, and I want it to be very obvious which group I am currently working with at any time. If they can't give me that, I'm not interested.