I think you misunderstood me. I used Kindle/Amazon as an example, but it was in reference to Apple's recent rejection of the Sony app from the iOS store. I haven't seen (nor mentioned) any requirement for the content to be available on iTunes. If that's the case, it's another issue altogether, of which I'm unaware.
http://www.nytimes.com/2011/02/01/technolo...apple.html?_r=2QUOTE
Some application developers, including Sony, say Apple has told them they can no longer sell e-books within their apps unless the transactions go through Apple’s system. Apple rejected Sony’s iPhone application, which would have let people buy and read e-books from the Sony Reader Store.
Apple said on Tuesday that it was still allowing customers to read e-books they bought elsewhere within apps. For example, a Sony app could still access books the customer bought earlier from Sony’s store.
But Steve Haber, president of Sony’s digital reading division, said on Monday that Apple had told his company that from now on, all in-app purchases would have to go through Apple.
QUOTE
Apps like the Kindle app from Amazon.com and the one that Sony submitted open up a browser window when a user wants to buy something. This allows the app makers to argue that technically the purchase is happening on the Web, not within the app.
Apple is now saying the app makers must allow those purchases to happen within the app, not in a separate browser window, with Apple getting its standard 30 percent cut of the transaction. At the moment this applies only to e-book purchases.
At the moment, the Kindle app is still available, but there has been speculation about its future as well, since it functions the same way the Sony app did - opening a web browser window for purchases rather than having the purchases "in app" and a cut going to Apple.
As for Sony pulling music from iTunes, Sony exec Michel Ephraim is now saying his words were twisted.
http://www.pcworld.com/article/219482/ok_e...and_itunes.html