“Our philosophy is simple—when Apple brings a new subscriber to the app, Apple earns a 30 percent share; when the publisher brings an existing or new subscriber to the app, the publisher keeps 100 percent and Apple earns nothing,” said Steve Jobs, Apple’s CEO.
Sure, if Apple brought in a customer then they deserve a cut. But they didn't. Apple didn't develop the app, Apple didn't promote the app, and Apple didn't try to sell the subscription. All Apple did was develop the iOS platform, and that doesn't count as bringing in a new subscriber.
It gets worse, actually. Apple also killed off any chance that we might see a reading app that only reade ebooks sold elsewhere:
Apple does require that if a publisher chooses to sell a digital subscription separately outside of the app, that same subscription offer must be made available, at the same price or less, to customers who wish to subscribe from within the app. In addition, publishers may no longer provide links in their apps (to a web site, for example) which allow the customer to purchase content or subscriptions outside of the app.
If we apply this same rule to ebooks, then this means that Amazon can't offer a Kindle app if the app doesn't sell ebooks.
On the upside, Apple's greed will push developers towards web apps, which will hopefully be platform agnostic.