Apparently, Facebook never, ever deletes your photos from its server. And not in an "oh, but they're just sitting inaccessibly on a dusty server somewhere" way -- in a, "if you have a direct link you can totally still access them four years after the fact" way.
Ars Technica reports that photos posted and deleted in 2008 are still accessible now, in 2012 (via direct link). Scary stuff, guys, because anyone can access a direct link to a photo for as long as it's on your Facebook page (depending on your privacy settings) and getting rid of your Facebook account entirely won't even fix that.
So...how about we all stop uploading stuff to Facebook for a little while, at least until they get this sorted out. In the next four or five years, perhaps?