The Thief and the Safe
An upscale thief, needing money to pay his income taxes, decided to hit the safe in a store. On the safe door, he was delighted to find a note reading: "Please don't use dynamite. The safe is not locked. Just turn the knob."
He did so. . .
Instantly, a heavy sandbag fell on him, the entire premises were floodlighted, and alarms started clanging.
As the police carried him out on a stretcher, he was heard moaning: "Alas, my confidence in human nature has been rudely shaken."