Its rapid growth at first appears unexplained by its revenue numbers, but the analysis done by Horowitz helps shed a light on this contradiction. Amazon simply yet efficiently re-directs all profit into further developing it's business. Of course, the answer to it's success is not so simple. As stated in the article, Amazon is really composed of many micro teams, which set their own prices and protocols. The logistics of running an organization like this are fascinating, and would require an article of their own.
What would be interesting would be to examine how the profits are re-invested. Does each team get a percentage? Are key areas identified for investment? How are these determined?