thecoalman - 2:30 pm on Mar 16, 2013 (gmt 0)
My worst error was was when I created a new sub forum, I had a bunch of forums I was using for classifieds that were not being used much and recycled one of them for the new sub forum. I moved a bunch of old posts into it... It was set to auto prune and before I had realized what happened I also backed up and deleted my old backup. <poof> went a few thousand posts.
I have comprehensive backups now so that couldn't happen again.