There are long endurance athletes who eat low carbs. Keith Norris and Mark Twight come to mind. If you don't know them, Google can help you out. These guys typically will go several hours a day on nothing but water. They don't hit a wall because there's no wall to hit. They burn fat from the beginning of the run to the end. (Keith cycles, Mark mountain climbs)
I would still argue that you wont be able to hit peak INTENSITY with low carb eating. On a long term races that's not really a problem, but when thinking about more intensive and nothing ultra long, carbs are the best fuel in my mind. Or if we get accurate, the combination of the two is the best fuel for victory. You just have to have pretty awesome skill to oxidize fat to beat carb-loaded fueling system. Just on the sole fact how much better do carbs turn to ATP.
Still, we have talked about this before, and I'm not denying the low-carb racing theories. That's just a piece of my mind.