In compliance with Apple's rules for the iOS App Store, Amazon recently updated their iOS Kindle app to remove the "Kindle Store" button. Previously, tapping that button in the app launched MobileSafari and loaded a mobile-optimized version of the Kindle Store web site. Books could (and still can) be purchased through that site and then accessed from within the Kindle app.
Dan Frommer argues that Apple's ban on in-app links to web sites that sell content is bad for users:
Now, Apple device owners will have to figure out on their own that they need to go to Amazon’s website in their Safari browser to buy stuff to read with their Kindle app.
This is a worse customer experience. Apple’s devices are now slightly harder and clumsier to use. And it’s Apple’s fault.
From now on, if developers want to sell virtual goods and subscriptions that don’t go through Apple’s in-app iTunes payment system — which forks over a 30% cut to Apple and puts developers at risk of patent lawsuits — they aren’t allowed to link to those other e-commerce stores in their apps anymore.
He's right: it's a much poorer user experience. But even worse, companies link Amazon couldn't sell their content through Apple's in-app purchase system, even if they wanted to. According to Apple's iTunes Connect Developer Guide (PDF), developers can only create "up to 3000 separate product IDs assigned to your In-App Purchases per app." Amazon's Kindle Store claims to contain "more than 950,000 Books, Kindle Singles, Newspapers, Magazines, Blogs, Audiobooks, and Games & Active Content."
Even if books represented only a tiny fraction of the 950,000 items in the Kindle Store catalog, there would be far more than Apple's 3,000-per-app limit. And even if Amazon were willing and able to pay Apple's 30% cut on Kindle sales and use the official iOS in-app purchase system, technical limitations set by Apple prevent them from doing so.
The end result, then, is a crappy deal for users. Forget whether Amazon can make money while paying a 30% cut. Forget the risk of patent liability and the investment of time and money required to start using Apple's in-app purchase system. The fact of the matter is, Apple has made getting books onto iOS devices harder. Users must magically know how to switch to MobileSafari and navigate to the Kindle Store, instead of tapping on an easy-to-use "buy" or "store" button. That doesn't sound like the kind of experience Apple wants to create. It sounds more like Android.