Kindle, I suspect.

Remember, this is being written by Tim O'Reilly, a person who has reason to know and care about the Kindle's position in the digital-text marketplace and the relative openness (or lack of openness) of the platform.

I agree that Amazon Web Services doesn't seem to belong on this list. AWS is a powerful offering, but it's not as if Amazon has an exclusive lock on the Linux virtual server business. I believe that even their provisioning API is in the process of being cloned in open source.