Werner Vogels of Amazon.com in a blog comment back in 2006:

"The best way to completely automate operations is to have to developers be responsible for running the software they develop. It is painful at times, but also means considerable creativity gets applied to a very important aspect of the software stack. It also brings developers into direct contact with customers and a very effective feedback loop starts. There is no separate operations department at Amazon: you build it; you run it."

(Via Sam Ruby and Don Box.)

Update: See also the in-depth article A Conversation with Werner Vogels (also from 2006).