1. Monthly subscription fee. Paying 60 or so dollars for a game that I can play forever is fine. Having to pay a fee once a month so I can continue to play the game is not.
2. I don't like to play MMO's anyway, as I'd rather not get addicted.
3. The entire population would consist of Battlemages, warriors, assassins, thieves and knights. Forget immersion.
4. http://elderscrolls.filefront.com/potd/75782x#1134024
5. The normal ES storyline and lore would be different in an MMO, mostly sacrificed in favour of a game focussed on team raids, loot and combat.
6. The quests would have no significance, because they'd just get reset for someone else to play.
7. What Rhayader said. It's better being a singleplayer game.
1) there are games without a monthly subscription fee (Guild wars, notably). Most games also give discounted rates to early adopters, and allow for a "lifetime" membership, which is something like 100$ to play the game for ever for 'free'. otherwise point is on.
2) MMOs aren't for everyone, but if you've never tried one its worth giving it a go. Most games have some sort of free trial without even having to buy the game.
3) Games typically have a pretty good class balance, which means that there is bound to be some Acrobats and Bards in there too (if they add all TES classes, which they should in an EQ like specialization system).
4) That picture was obviously not made by someone who has not played an MMO other than Run Escape. even the newbs in WoW's starter area don't talk like that. NO community is that bad. There is the occasional bad spelling and clueless newbie, but its no worse than anything you see in this very forum. Additionally, whole channels can be blocked, so you don't have to read conversation you don't want to. members can also be silenced individually. It may be funny to joke about how bad MMO communities are, but its a blatant false stereotype and offensive to the thousands of smart, mature people who choose to game online.
5) The storyline could still focus on the individual player. in fact, the accomplishments of the individual could be more dramatic, since he would be competing with thousands of other players, not level scaled NPCs. Besides, current TES quests focus on "loot and combat" as much as any MMO's.
6) Quests already have no significance, since they reset when you play a new character or when anybody else plays the game. Since you don't actually see other people doing "your" quest, this point is moot. As i've said before, the real-time nature of the MMO allows for quests with consequences that actually matter in the game world. quests could easily be randomly generated like in Daggerfall, allowing for endless (if somewhat dull) repeatability of minor quests. Major quests could progress the storyline of the world if completed (eg. if X people on the server find Person Y, Fang Lair becomes an explorable location).
Arena. Battlespire. Redguard. Shadowkey. Dawnstar. Oblivion Mobile.