Amazon doesn't use Mason externally, they use it internally to "prototype." Many books have clairfied this.

So it shouldn't be too hard to name one of them, right?

I can't find this anywhere on the web. As of a few years ago the story was that Amazon was using Mason quite a bit, and had plans to use it even more...

• Jonathan Schwartz
• Mason HQ

A number of sites use Mason: MasonPoweredSites