Thanks to Karthik who pointed me to this excellent interview of Amazon CTO, Werner Vogels. Werner talks about the loosely coupled ultra-scalable technology platform that Amazon is. Some particularly noteworthy lines:
Giving developers operational responsibilities has greatly enhanced the quality of the services, both from a customer and a technology point of view. The traditional model is that you take your software to the wall that separates development and operations, and throw it over and then forget about it. Not at Amazon. You build it, you run it. This brings developers into contact with the day-to-day operation of their software. It also brings them into day-to-day contact with the customer. This customer feedback loop is essential for improving the quality of the service.
With a new radical service, you try to go into prototype mode pretty quickly, and then you start iterating on that until you feel that you understand your business problem.