This remains to be seen. They have been working on it just in a really crash, burn and restart process way. Mark Zuckerberg once went through two options for public discourse
* create a Facebook fan page
* open his personal profile to public
The first attempt was silently killed (from what I can see, this is my assumption) and now redirects to his personal page (www.facebook.com/markzuckerberg -> www.facebook.com/zuck). The second attempt, well, as you can see from his profile, it is pretty much closed up now.
Private sharing, as least from the friends I have, has been going on pretty frequently, just not on the timeline
* private groups
* group messages
With messages, it seems Facebook is testing inline message (1) along the status composer (on the homepage) which aligns with the thinking that they are making private sharing less restrictive to action on while maintaining "privacy" (in quotes, as some may not agree to the level of privacy offered)
I have no data to back up how effective private sharing is though.
(1) http://techcrunch.com/2013/06/02/facebook-status-composer-me...