It's not easy being a Game Master in real life (unless you have a really good role playing group and let's face it, even they kill a couple of important NPCs once in a while). It's no cake walk in Knights of Pen and Paper +1 Edition either, but at least none of the players can leave in the middle of a boss-fight because their dinner is getting cold.
If you've played a role playing game, what's the stupidest thing you're group did that annoyed the GM? I've once fed an very important NPC to a werewolf as a distraction.