That's true, many bigger companies do shave. That's something we all have to work with, either networks or direct publishers. They never admit shaving, though, often saying something like 'check if your targeting is correct'. Thus we, as a network, have nothing to do but tell the very same thing to our publishers. Also, if you see huge difference between one and another network's payout for the same offer, there is big chance that the one with higher payout shaves.