I was just idly wondering, seeing as so many people profess to want more consequence for ingame actions...

...how would you react to a main quest that you could actually fail? As in, you failed such-&-such a task, now the MQ is finished and such-&-such is the consequence. Would there be any market for that kind of ingame consequnce, or is it too alien and non-gamey?

In fact, it seems to me that there aren't many/any quests that CAN be failed. Quests that are unfinished yes, but actually finished, but failed?

I know there would always be the reload option, just tossing ideas around.

Martin could die in Oblivion, let's not remember that, if Martin died during the battle of Bruma, you effectively failed the entire game... I can't remember if it just failed the MQ or if it killed you off...

The world would be eaten, and I can't imagine that would be very fun

Well, considering that the consequence for failure would be Alduin destroying the planet, I would say there probably isn't much market for that...

Well, Oblivion was reloaded to newest savegame if Martin died.
Morrowind allowed you to kill anyone, effectively ruining quests.
Skyrim, not so much.

...unless there was some other, non-player hero who DID complete the quest

Would be quite a humiliation, being a follower for that awesome NPC

Yeah, no fun to lose. Better to just leave a "game over" screen than put effort into it. I wouldn't be against developed consequences to MQ failure, per se, but why waste resources when you could put it in something fun?

you had to reload a previous save

You can fail some quests in Skyrim.

You could technically fail in mass effect 2...