I play (off and on) a fair amount of Diplomacy online. I used to play just with friends, but sometimes I play with strangers at http://www.playdiplomacy.com
(which is a great site if you like the game).
My last game with friends ended with people quitting, and my girlfriend refusing to ever have anything to do with my crazy-gamer friend ("I don't care if he apologized, I don't ever want to meet that guy") . Another friend of mine has sworn off playing with the rest of us forever. And I'm currently in an internet game with people I don't know where I argue with one of the other players because he keeps telling me to "Take it easy" and "Calm down" whenever I send him what I think are perfectly bland, non-upset Diplomacy messages.
But I don't think any of these people are wildly dysfunctional. I think there are such hugely varying ideas of "How You're Supposed To Play" that people come to the table with very different expectations of the game.
Many people feel that in Diplomacy *ANYTHING GOES* ... there is no such thing as cheating, unsportsmanlike behavior, dishonesty, etc. Which sounds weird, but it's very common. And if you are in a group where everyone thinks that, it works great. But when you combine those players with different kinds of players, social mayhem ensues.
With the guy I'm playing with now, he sends almost no messages. Which to me is a crazy way to play the game. But to him, my multiple "Hey, what's up with your move?" messages apparently make me seem insane and histrionic.
I guess I have no real point here, other than to say that Diplomacy (while not a role-playing game per se) illustrates better than anything else the idea that a game is made up of more than the written rules, at least to me.