[chromatic]

For how many years did Amazon lose money on every customer?

Fewer than most people think. Consider the financial model of a (successful) grocery store ostensibly losing a penny on each transaction. If you're clever, you can make plenty of money by arranging your contract terms carefully.

[webwright]

6 years is the answer to my rhetorical question, if you're curious. Groupon is less than halfway to that point, and has much higher gross margins than Amazon did at the time (and about 2x what Amazon has right now).