Here's a lighthearted failure suitable for Friday afternoon.
In a true "sign of the times", so to speak, someone reprogrammed an electric highway sign to warn motorists of impending zombies:
CAUTION ZOMBIES AHEAD!!!
THE END IS NEAR!!!!!!!!!
RUN FOR COLD CLIMATES
Here are the photos:
Update 1/30/09: The screens are manufactured by Imago. Looks like the signs run proprietary software and operating system.
These machines are programmed by a keypad located inside a compartment that can be locked. If the compartment isn't locked, thereby giving physical access to the keyboard, anyone can get inside. Although the manufacturer assigns a default password to every unit, many owners don't bother changing it. Therefore, reprogramming can be a simple matter of opening the unlocked unit, entering the default password, and typing a new display message.
In a sense, this can hardly be called a hack. It's really physical intrusion and takeover without any special feat of programming skill.