Take the recently announced Elder Scrolls Online for example. I love The Elder Scrolls games, however I love them for all the reasons that it will never work in an mmo.The biggest problem that always faces a mmo developer is how to balance players and the game world. When I am playing Skyrim, I am free to wander off in any direction I want, and face challenges with a wide choice of skills and abilities in any order I fancy. However I can't see that ever happening in a mmo, because how do you balance having high level characters and a low level character wandering around the same area. How do you cope with pvp, what if 5 people turn up at the same cave at the same time, how to character skills interact with each other. It is for this reason that all mmo's have groups of enemies just milling around a fixed location, waiting to be killed.
Guild Wars 2, for all it's brave promises, has still kept classes and, loosely, the DPS tank healer paradigm that has been around for years. It is, I believe, impossible to have a giant open world rpg mmo. In fact The Old Republic proves this very notion. despite there being a wide range of planets, go off the beaten path and you will get killed. You get quests to got to very defined area's where enemies are stood around, I assume chatting, waiting for you to turn up and kill them. You have to go where the game tells you, when the game tells you. This is not a criticism, as they have made the story so enjoyable that you forgive it for being as linear as the average Call of Duty game (though much much longer).
There seems to be this believe now that multiplayer automatically equals success. I guess Bethesda have been eyeing the money that Blizzard makes for long enough to get envious. Having just played Secret World which turned out to be a uninteresting game in an interesting world, I have decided that The Elder Scrolls Online is not of interest.
However it sure as hell explains why Bethesda fought Notch over the rights to use the title Scrolls.