Apple may have forced Amazon to remove the option to buy books from within its Kindle App, but Amazon isn't taking it lying down; they're building a web app that could possibly replace the iOS apps altogether.
The Kindle Cloud Reader is already live for users on Chrome or Safari, including the iPad version of Safari. It lets you keep your books in the cloud or download them for offline reading, all within the browser. And it looks pretty slick! Not to mention the nicely integrated Kindle store, which is conspicuously absent from the App.
You've gotta wonder if Apple is rethinking its move to try to squeeze money out of in-app purchases like this. One would think that they'd rather have apps going through their store rather than be out there online; if people start abandoning the App Store for web apps, they lose the tight control they've kept over what can run on their mobile devices. We'll see!