Cheers for the mention ADH – the image in question:
I think it's technically quite a weak shot – I've only got a 450D, a 10-22mm and a mid-level flash gun + diffuser. I think the flash is a bit 'hot', it's a bit contrasty and I always get the forward motion blur despite using second curtain flash syncing. But at the same time, like what PP is saying, it does a much better job of capturing the moment.
However, clearly the guy in question is coming at this from a purely commercial aspect. He's obviously worked out he needs to get every rider, and at least 4 photos of each, he'll know from experience how many photos will sell and it's probably a nice little winner for him.
I on the other hand while happy to lay down in the bushes, an inch from your wheel, wielding a 10mm lens, and generally risking a dam good clattering from the next rider who crashes, will probably only hang around for a couple of hours, only capture a fraction of the riders, shoot in fewer locations and probably throw away more than half the shots I take.
So I think it's unfair to batter the guys who do this…