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.
I 100% think that this is what is happening. Before Facebook's chat feature became as prominent as it is, the number of 'trivial' wall-to-wall posts was very high, such as 'hey, what what you been up to?' or 'Thanks again'. These posts look like 'messages' because these days you would normally just send it as a message.
Yeah, I'm really certain too. Some of them seem surprisingly private though, so no wonder people get scared. It's still a bad thing that friend banter from long ago suddenly shows up for all your new friends / colleagues / family to see...
This is exactly what I'm seeing. I just spent half an hour on the phone with my friend going over public posts from 2007 saying "WOAH, did we _really_ say that in public?". Every one was public. There were no examples of private messages showing up.
