So as this has somehow mutated into "philosophy week" on Tobold's Blog, I'd like to explore further the philosophical notions that "this is just a game", "morality / responsibility doesn't apply in a game", and "I'm here voluntarily, so I should have complete freedom of choice". Let's accept these notions for a moment, and see where that leads us in a thought experiment:
Think of whatever you hate most in the behavior of other players in World of Warcraft or another MMORPG: Naked night elves dancing on mailboxes, ninja looters, people not moving out of the fire, whatever. And now think what you would answer to somebody defending that behavior you hate with "this is just a game", "I don't have any responsibility here", or "this is my freedom of choice". Why would anyone have a responsibility to not deliberately wipe your group, or to do over 1k damage per second when playing a DPS in a heroic? If you have total freedom of choice over what to do, what would keep others from having that same freedom of choice and using it to do things that you hate?
I believe that everybody's freedom ends where the freedom of the next guy begins. Thus in every activity involving more than one person, even if it is "just a game", there is some sort of responsibility involved. Because everybody having complete freedom of choice is by definition anarchy. Freedom of choice must have certain limits, and these limits are somewhere where your freedom impinges on the freedom of others. Now of course we can have an endless discussion of where exactly these limits are, and whether your choice creating a waiting queue in the Dungeon Finder isn't harmless enough to allow that freedom. But I can't accept total freedom of choice without limits, not even in a game.