I don't think any of the big (or small) corporations should be trusted, but in the case of Amazon, the question of trust in connection to data is much bigger than trusting them not to abuse powers from having SSL certs in the browser. They already run a huge part of the infrastructure of the Internet, and have the possibility of reading the private SSL keys of a number of services by virtue of hosting them.

The CA system is broken by design, but I don't think adding Amazon will make much of a difference either way.