I too thought I found private messages on my timeline. But it turns out they were indeed wallposts. It shows how much facebook has changed from a friends-only environment where you used the wall of people for semi-private chats, to a place where you have to be carefull and try to present yourself in a decent manner. Noone would ever use the wall in the same way it was used back then.
So much press on this 'bug' but so little proof