An UPDATE without a WHERE clause that doesn’t get noticed for a week or two. Your data’s hosed and you can’t really cope with reverting to your last known good backup. Bonus points if you haven’t tested your recovery procedures recently. Then he runs around screeching about how the data is obviously fraudulent and he’s a genius for finding it.

Little Johnny Tables, the hero we didn’t expect.

Oh I just curled up into a fetal ball at the thought of that…