I noticed it as well just now. You find it past 2011 near the top of the 'year' It's a box that says 'Friends 2011' or whatever the year is, and is a compilation of posts made to you. Some are just wall posts, like birthday greetings, but I noticed random PM replies mixed in. That is evil. I've removed them all from timeline and will be checking my friends pages as well and posting a general notice about it on my page.
Thank you to the OP for bringing this to attention! Most people don't look past the current year on their page.
And I stopped trusting FB long ago... don't post any personal info to anyone anymore and only PM basic conversations now, but still... geez, what they won't sink to next. Main reason I'm still on it is because so many of my friends are as well it's the only place I can contact them.But personal stuff is in the past!
Again, thanks for the heads up!