Once you checked out the video I linked to in my previous post, it is an interesting excercise to apply Clint Hocking's generation conflict theory of video games to the narrower field of MMORPGs. The original Dungeons & Dragons pen and paper roleplaying game, published in 1974, is very much a product of the baby boomer generation, being all about free interaction between players.
The generation X version of roleplaying was Everquest: punishing, and abusive, and all about achievement, and beating the fixed challenges of the game. But EQ had inherited a social component from D&D, almost involuntarily: If you create the Matrix in the generation X style as objective reality against which players bang their head, the real-life fact that doing something together is usually easier than doing something alone invariably sneeks in. The more punishing and abusive you make the virtual world, the more players are forced to play together, to cooperate. But generation X is a generation of lone wolfs cherishing their independance, and so they called this feature "forced grouping" and hated it.
World of Warcraft started out with a generation X base, but with the knowledge that players hate forced grouping. So the generation X loner's dream of a massively single-player online RPG was created. But of course if you have a game in which grouping is possible at all, and in which you want to enable soloing, this turns out to be incompatible with the generation X idea of games having to be punishing and abusive. You need to lower the bar for single players to be able to overcome the challenge, because the minute they can't get over a hurdle alone, they'll group up. In the end the only way Blizzard found to make content that was hard, was to create instances with a limit on group size. Note that in vanilla WoW group limits weren't totally fixed yet, you could still do Stratholme and Scholomance with 10 people, or UBRS with 15.
I think it is best to see World of Warcraft as a game between generation X and generation Y. The lowering of the bar necessary for generation X to solo it, simultaneously fulfilled the generation Y condition of a game having to be more accessible and forgiving. If you compare other features from Everquest and WoW, you'll find more generation Y influences: The death penalty has been lowered significantly, and gameplay is guided by handing out a steady stream of rewards from quests. World of Warcraft being a game with both generation X and generation Y influences makes it both successful, because all generations want to play it, and a battlefield of the generation conflict. As Clint Hocking predicts with his demographics, generation Y appears to be winning that conflict, with WoW definitively moving towards ever more forgiving gameplay, and handing our rewards to everyone for participation, not just top performance. The increase in social features, like the patch 3.3 new group finding system and the Cataclysm guild cooperative features are pure generation Y.
Nevertheless, the generation X roots of World of Warcraft are too strong to ever turn it into a pure generation Y game. Which is where Blizzard's next generation MMORPG comes in. People often wonder how Blizzard is planning to make a next generation MMORPG without canibalizing the WoW user base. I think part of the answer is that the next generation MMORPG will be very much a generation Y game, with little generation X influence left over. I expect the next Blizzard MMORPG to be a lot more cooperative, with a lot more social networking than WoW has, and with a lot less of the generation X aspects of players trying to overcome static challenges. Of course generation X players will hate that game, and deride it, but by the time it comes out generation X will be past its prime anyway, especially in the teen to young adult age group most likely spending their time in virtual worlds. The next generation Blizzard MMORPG might resemble A Tale in the Desert and Facebook more than it resembles Everquest.