It's always been an unwritten rule (at least in those places I've chosen to frequent) that, even if all other bets were off and you were ripping into someone in the cruelest possible manner, you left real life out of it.

I actually left a community because one of the members kept threatening to bring his...anger issues into real life.

Pranks, flames, and embarrassments online are one thing; crippling someone's ability to make a living is quite another.