I've always wondered this: I know when you mount a drive (USB stick, FireWire external or even an iPod of some sort) in OS X, a few invisible files get created. And if you have an AV program, sometimes it will write files to the drive. Same with some other third party apps. Do any of these files contain personal information, or things unique to the machine? Like user name or directory structure or things of that nature? I assume they don't, or else you'd probably see it mentioned more often, but I was wondering if anyone had a definitive answer..?