Ya know, gibblet, the heck of it is that you have to dive off into fluid dynamics and thermodynamics to get the rules for a lot of this stuff. I certainly get in way over my head sometimes, cuz I ain't no nerdy mathmagician, but basic physics don't get the job done. [&:]
Actually some argue there is another advantage to putting on a lighter faster arrow and that is that you will reduce the time the arrow is in contact with the string during acceleration thereby makeing the bow a little more forgiving to shoot.
There's another point where I see a huge fallacy. I agree that any effect would be minimal - if even discernable. Even though time is slightly reduced, the distance the arrow remains on the string remains the same.
As for time, let's compare a 250 fps arrow with a 300 fps bow. Assume a 30" draw with a 7" brace height. About average brace these days, isn't it? You're left with a 23" power stroke. Of course, these numbers aren't going to be exact, because we're not figuring in the arrow's inertia on the rest and time the string takes to overcome that inertia....
So don't jump my stuff about it! 
The 250 fps arrow will be off the string in 76/10,000 ths of a second. A 300 fps arrow will be off the string in 64/10,000ths of a second. I just don't see a whole lot of forgiveness in 12/10,000ths of a second.
Factor in the reflexed risers manufacturers have gone to in order to increase arrow speeds, and how easy they are to torque, I see no forgiveness advantage, whatsoever. There's a reason I prefer deflex risers, even though they can't shoot an arrow as fast. They're extremely hard to torque and ultra forgiving. Darn shame there are so few made any more.[&o]