I think Amazon is simply reinvesting in growth while avoiding corporate income taxes. Since they tend to move into proven industries, they are not likely to lose any of the re-invested money.
They are effectively taking profit in the form of Amazon equity (via increased stock price) and not paying any taxes.
I don't have a problem with that... imho corporations should be working to either grow (reinvest or diversify) or payout dividends... I'm pretty opposed to a corporation holding on to vast unused/underused properties and cash reserves. It does nothing for the communities they take hold in, or for the economy at large.
They are effectively taking profit in the form of Amazon equity (via increased stock price) and not paying any taxes.