Originally Posted by chicagorich
But--normally, when a company sells a product--it has incurred its production costs to sell their product to you before you buy it--and usually the company has no further obligation to you except in a warranty.
This is a key point. There are no real costs to speak of until you redeem you miles, and who knows if that will actually happen. Until then, the obligation shows up as a liability.
There's no inherent reason why you couldn't make a good business out of this if you were conservative, but the financial pressure to undervalue the accumulated FF miles (the liability) must be tremendous.