Geez, oh yes. They built their platform and decided to start reselling it. That's why Netflix, Pintrest, Airbnb, Expedia, Foursquare, NASA, the MLB all use AWS.

They converted 100% in 2011 according to Jon Jenkins https://www.youtube.com/watch?v=dxk8b9rSKOo#t=449

Most, but not all of Amazon.com runs on AWS.