Are non-public Game Center Profiles not listed in "friends in common"? I understand that one can configure a Game Center profile so that it is only visible to Game Center friends. Are such profiles also not listed among "friends in common"? 

I have several friends, most of whom I have each other in common with me, but when I select the their lists of friends, I see no friends in common.
In the current, iOS 5 version, of Game Center, in order for friends in common to appear (as "shared friends"), they must also have upgraded to iOS 5 (and have accepted the new ToS).