my contention is that as the tread mill speeds up it will create more friction on the wheel and thus more drag on the plane, keeping it stationary. think of it this way. if you hold let's say a bicycle wheel(by the axle) against a belt traveling 30mph then it should be harder to keep in place than one against a belt going 10mph.

I'm doing a shitty job explaining this, oh well maybe someone will understand what I'm saying.