Unless I'm mistaken, data goes from web server -> Amazon -> Kindle Fire, not server->Fire->cloud->Fire. The whole point of rendering in the cloud is to reduce latency by having fewer requests over the cell network.
Absolutely. And I'm sure raganwald knows that. By "pushes it back up to the server", he didn't mean that the Fire pushes it to the server on a request-by-request basis; he meant that conceptually Amazon has moved the locus of rendering (again).
