And get this -- when Apple sells you a "new" drive to replace the broken one, at 1.5 times what it would cost mail order, how much you want to bet it's someone else's broken hard drive that they got for free.
I've personally run some recovery programs on a Samsung replacement drive I received (from Samsung, not Apple) and I was able to recover files that presumably belonged to a previous owner. I didn't bother checking if it contained any personal information (I was only interested in recovering a corrupted dotfile), but it seems possible that sensitive information could have been contained on said drive.
