Are MMOG's unable to foster good, positive, enjoyable communities?
Well, the question becomes, "what kind of player does your game generally attract in the first place"? It has been my experience that griefers and jerks gravitate to games and game situations where they can force themselves on others, and where others need them, and where their unsocial (at least, in real life) ability to obsessively avoid the outdoors and real relationships and keep their butt parked in chair in front of a computer for hours and days on end makes their character desirable, or even necessary, to accomplish necessary game content.
Current MMOG game structure demands that end-content driven players get their sense of satisfaction, achievement and respect from the game, or else they would not be willing to dedicate themselves to achieving end-game content - they wouldn't be willing to invest the necessary marathon-like investments of time.
Are these people psychologically fit for any kind of community relationship, any kind of social dynamic other than one based on how much time you're willing to devote to the game, and how willing you are to conform to maximum in-game efficiency? Don't you think there is a reason these players are substituting the MMOG for an offline social life, in many if not most cases?
The problem is that the very structure of current MMOGs are built to attract and singularly reward what cannot be viewed, overall, as a healthy, well-adjusted social psychology. This is why so many people here make the absurd claim that community=forced grouping; they can't conceive of people regularly and happily grouping up and doing things unless they are forced to.
This is why you see so many people here state that there is no reason to play an MMOG unless one is devoted to spending marathon amounts of time and effort to advance their character; they don't understand people that play for other reasons. They simply don't understand why those people, who are not happy about being forced into groups with them, don't just go play solo games; for the players current MMOGs are basiclaly built to attract, community=forced grouping built around single-minded devotion to advancing in the game.
Is it really any wonder that a genre built around these kind of people has failed so completely in generating good, solid, enjoyable communities?