Apparently, there is/was a bug that showed private messages on timeline? Here is the article I read, it is dated 9/24/2012
http://www.huffingtonpost.com/2012/09/2 ... Technology
I lol'd because I don't really like facebook much anymore, but was pissed that my wife read all of my personal messages. Needless to say, I went ahead and deleted my facebook account.