One of the new features coming in iPhone 3.0 is the capability for an app to have what I'll call sub-purchases. The example given was a game you'd buy and then, from within the game, you'd be able to buy additional levels. Currently you have to buy a different version of the game, or get an update - which so far have been free.
But one point about this new feature is that you can't buy add-ons from within a free application. A developer can't give away the razor and sell the blades.
Why is that interesting? Well, Amazon gives away their iPhone Kindle app, but sells content.
If I were Amazon, I think I'd like to walk away from the whole idea of the AppStore. Amazon has a delivery mechanism. They can handle micro payments. They want to give away their iPhone Kindle app and have you buy books from within it.
But they won't. Why should they give Apple 30% of each book sale? Their current model (the iPhone Kindle book sees everything you've purchased from Amazon, but you have to do the purchasing via a web page or a 'real' Kindle) will likely continue.
The AppStore is problematic at best. The whole idea of a cadre of Apple employees passing qualitative judgement on apps is astonishing to me. How can Apple seriously reject an iPhone app for obscenities when I can buy, literally, the 7 words you can't say on television on the iTunes 'Music" store?
The AppStore is probably great for the one-person shops who are developing an app in their spare time. It's probably even helpful for an entity like the New York Times, which lacks a software distribution infrastructure. But Amazon doesn't need their help.