Yeah, part of me wonders if the Ur-Fic for an OTP necessarily requires a certain amount of output. I think it's possible that there is the one Ur-Fic that draws people to a fandom in the first place, the one that acts as a blueprint for all other fics in the fandom. I think for the most part, the Ur-Fic usually will evolve after that to become more distilled, but maybe it never drifts very far.

As to whether or not any Ur-Fics end unhappily, that's a good question! I think there may be small OTP fandoms with an unhappy Ur-Fic. There was one I was in where one half of the pairing dies early on in the series, leaving the other half to mourn him. That death played heavily in the fic that tiny corner of the fandom produced, but it's hard to say if it ever got big or connected enough to create a proper Ur-Fic.

Fandom abhors unhappy endings, so I seriously doubt it works for any good-sized pairing.

Hour/Foreman: Heee!