I have been experimenting with some different weigh arrows, and regardless of weight, one thing is constant- hit a big bone and I dont care what your arrow weighs, you're in trouble.
I am currently shooting some Lam.Birch shafts that weigh 620. They are only 30 gr heavier than my pine shafts, fly wonderful, but really start to drop at about 20 yds.
Like others have said, where the problem comes in is trying to push for the lightest/fastest setup. It may work fine for whitetails, but wehre the problem begins is those who would try that same setup for elk or other heavier-build critters.
For me, I primarily hunt deer, where lighter cedar shafts would be fine(450-500gr) but didnt want to have to adjust from one arrow to another elk or deer. I went to the heavier shaft for everything.
So far so good.