Amazon makes extensive use of capital leases support their expansion. In 2014 they were roughly on par with their other capex (in the $4B-5B range, don't remember exact number), except that their capital leases don't deduct from Amazon's free cash flow. If you subtract those out, the FCF situation ends up looking quite a bit worse.

http://seekingalpha.com/article/2743335-understanding-how-am... and http://www.fool.com/investing/general/2015/02/04/amazon-just... discuss the mechanics.

They're sort of taking on a bunch of debt (or things that look like debt) and downplaying it with clever accounting. In the current market environment I don't know that it's really a problem (they just borrowed $6B via a bond issue, for example). Just an interesting reality for a company competing with two cash-rich rivals in a hugely capital-intensive space.