You should read this thoughtful article comparing Apple’s iOS App Store, Google’s new One Pass system and the Kindle ecosystem. It’s essential background to the current kerfuffle in the publishing world.
Just one quote: “Apple is insisting that the customers it brings to publishers via iTunes should not be forced to give up their personal data to the publisher.” Quite right, too. Who could disagree with this except the publishers?
Here is a convenient run-down on the three systems (table courtesy of AppleInsider).