... The TES fanbase are the kind of people who would actually boycott a game for something like that though :3
I would not boycott it.
You people act like its more a technical impossability. Saying "What if 2 people try to turn in the same quest?" Well, then they both complete the quest... whats there to be confused about? Each player would have their own quest log, their own skills, essentially everyone would be independent, except all in the same world. (Co-op, not mmo).
Ironically TOR shows that a campaign based, dialogue heavy game can work with more then one person. Quests involving killing NPCs have their own instance that you can freely run in and out of (No loading screen) and is independent of other players. Anyone you are grouped with, share conversations if they opt to.
The fact is, it can be done in a way that does not detract from TES's depth, but you are all to arrogant and wont even consider the possibility of a [censored] option.
If I recall, many people were wanting options for everything before the game came out, but here, everyone is mostly set on it being an absolute no.