One of the truly sacrosanct beliefs in the greater MMO community (which includes both developers and players) is that achieving balance between classes is a necessary ingredient for a successful game. Even though the relative power of classes is liable to swing wildly depending on the latest patches and play styles, the goal is always to achieve that perfect (and largely fleeting) point at which classes are more or less equal. According to Eric over at Elder Game, achieving balance shouldn't be more important than making a game fun to play.
While Eric's post was directed primarily at system designers currently in the employ of game developers, we think the lesson should be well-learned by players as well. Few things turn otherwise nice and friendly people into sniveling, pedantic jerks quite like the knowledge that the way they choose to play the game isn't perfectly balanced with whatever the flavor of the month happens to be. Isn't it enough just to have fun playing? Or is fun inextricably bound to one's relative power? We'd like to think that's not the case.