Neither is Amazon as I understand it.
>It is being hosted on Google Docs.
Amazon is just printing the book.
>This is no different than if someone put the PDF on Dropbox and made it public.
This is exactly what's happening on Amazon. Someone uploaded the pirated file, as their own. Amazon is simply printing the book, and helping you find it via a search interface. I'm still failing to see a distinction here between what Google and Amazon are doing, beyond the fact that Google's approach is digital, and therefore zero cost.
Both Google and Amazon benefit from the piracy. Amazon directly through sale of product, Google directly through search ad revenue. Both Google and Amazon provide the platform for the piracy. Both Google and Amazon provide search discovery for the pirated product.