Way way back in the day, my friend wrote a program that would format the user's Commodore 5 1/4" floppy disk (usually the one that also ran their BBS) if they just tried to load it. They didn't even have to run it.
If someone screwed us, we'd create a new identity and upload a file named after a hot new pirated game to their BBS. Then sit back and watch the BBS go offline for a while.