Bezos quotes an article about AWS, "..in fact Amazon's real business down the line will be its cloud services. Amazon will be like a bookstore that sells cocaine out the back door. Book will just be a front."
Another point I recently heard, and I can't recall the exact quote off my head but it was along the lines of: "Amazon at this point is really just a cloud company that is using it's cloud earnings to subsidize its other business arms to grow to a big enough scale where it can choke out all other competitors."