The mechanism is the managers that take over at companies who focus on the short term bottom line (trimming support today, to juice profits tomorrow, to lose credibility years down the road after the bonuses have long landed in their bank account).

And the problem is that Amazon's growth profile (retail-side anyway) is going to be pretty constrained going forwards because they own too much of the available pie right now. So the result is that managers are going to have to look for other ways to trim costs to make numbers.

If you're starting from 0.001% of the retail market and trying to grow 10x it is much easier to do that just by having really good customer service.