If you view computer programmers as mental ditch diggers, then the idea that one could be so much more productive than another seems crazy. But when you see it as a creative endeavor, it's completely rational that some could be orders of magnitude more productive, even infinitely so.
For example, when you have a hard problem (like a networked 3d game with physics) that is beyond the abilities of a developer A (he can't solve the problems at hand, no matter how much time given), but not developer B (a creative thinker who can solve the problems quickly), then I think you can literally say Dev B is infinitely better than dev A for those hard problems. Because it's going to take you infinitely many developers A's randomly poking at their keyboard to solve the problems. But dev B will solve them in a reason amount of time.
Now dev B isn't infinitely smarter, but for certain tasks, he's infinitely more productive. The point is the productivity differences are highly context dependent, and the greater the creative and cognitive load of the tasks, the the greater the measurable productivity differences between the highest and the average developers.
1) Knowledge is entirely linear. If there some tasks programmer A fails at and some tasks programmer B fails at, then all you have is an apples-to-oranges comparison (which is what a lot of the x10 chest-pounding comes down to).
2) Knowledge isn't shared in the group. My proudest moments have involved actually teaching my co-workers how to write a recursive descent parser, why ACID matters in databases or how to divide a multi-threaded application between worker and consumer threads. It might be true that if I'd just kept my knowledge to my self and laughed as they failed, I might have been a 10x or even a 100x programmer. But it was more pleasant and satisfying to be the guy who actually helped everyone.
Slight nitpick: Infinite developer As will not solve the problem unless you assume that each developer can solve a finite part of the problem. If Developer A simply can't solve the problem none of them will help.
For example, when you have a hard problem (like a networked 3d game with physics) that is beyond the abilities of a developer A (he can't solve the problems at hand, no matter how much time given), but not developer B (a creative thinker who can solve the problems quickly), then I think you can literally say Dev B is infinitely better than dev A for those hard problems. Because it's going to take you infinitely many developers A's randomly poking at their keyboard to solve the problems. But dev B will solve them in a reason amount of time.
Now dev B isn't infinitely smarter, but for certain tasks, he's infinitely more productive. The point is the productivity differences are highly context dependent, and the greater the creative and cognitive load of the tasks, the the greater the measurable productivity differences between the highest and the average developers.