Yet, how do you tell when Amazon are about to do that? I would've thought they'd do it when revenue growth starts slowing. ie. When the strategy of spending money to make money starts being less effective, as there is steadily harder gains to be got from it. That's when I'd turn on the tap.
So just as Amazon are about to do this (potentially anyway), that's when people sell? I'd say this is by far the best time to buy...