Be careful, don't get drawn in.
Okay, fine... If nobody else is gonna get back to business, I will.
Someone goes and books lots of hotel rooms/award tickets (let's say for argument's sake, he is Plat so he gets free redeposits) for prime dates. He then offers to people that he will "sell" them the availability - i.e. in return for a fee, he will cancel his reservation so that the "buyer" can snap up the newly-available date. Is it ethical?
My 2 cents: no, it's not. It's like domain name squatting. If he booked those dates planning to actually use them, and is now considering the hassle of altering his plans in return for some compensation, then
maybe it's okay; but to book for the express purpose of "reselling" the
availability (remember, we're not talking about the actual stay/flight - just the ability to book it with your own points) is just plain evil.