The “split browser†notion is that Amazon will use its EC2 back end to pre-cache user web browsing, using its fat back-end pipes to grab all the web content at once so the lightweight Fire-based browser has to only download one simple stream from Amazon's servers. But what this means is that Amazon will capture and control every Web transaction performed by Fire users. Every page they see, every link they follow, every click they make, every ad they see is going to be intermediated by one of the largest server farms on the planet.
