I think the example of multi's on webdiplomacy is a great one. Their behaviour ruins games for the rest of us. They have a very different idea of what they want to get out of this game, just to win, and they see cheating the system as a challenge - thus by winning and getting away with it they are not just winning at a game of diplomacy they also managed to con people they were playing with...

But the question remains, why should we expect people to NOT cheat, at anything... humans by their very nature search for the easiest solution to any given problem. And diplomacy games are hard, they pose a challenge to those who try to win.

(those who cheat end up winning with ease, and thusly either get bored or try to win even more, because there are points to be gained!!! but the value of what they have earned is much less because it took less effort to gain... hence the boredom, or escalation to a new level, the attempt to earn lots of points)

So if humans are natural cheaters, then why do so many of us NOT cheat in the first place? - i hope this game illustrates the pointlessness of cheating: http://www.maths.tcd.ie/~orathaic/multiswebdip/

So many of us live with a world-view where we are mature enough to realise that making something easier will remove the challenge and thus reduce how good we feel about winning - either that or we were taught that cheating is bad and are far too polite to consider such a thing... but i'd imagine most diplomacy players have considered life enough to have a slightly deeper understanding then that of why you'd choose to not cheat...

So, is it their fault that they cheat/multi/meta-game? or is it the world-view which they have and that nobody has bothered to explain/coerce/convince them??

Equivalent to inner city gangs who have a very different world-view, and value system.