Wow, and people talk about the "Microsoft tax". How long until the only way to get software on your Mac desktop is via Apple's store and all Mac developers are required to pay a 30% tribute to Apple? And, since taxes are passed on to consumers, every time you as a customer buys an "app" from the store it's really you who's paying that insane 30%.
Let me preface this by saying that I am against the one-company-to-rule-them-all model that Apple seems to adore. And one of the reasons is exactly the point you bring up above. However, I think there is something to be said about the user experience brought about by having one company (in this case, the platform and hardware developer, Apple) whose feet are ultimately held to fire for the quality of the applications that are available to end-users on their platform (yes this does and WILL apply to Apple).
To illustrate, let me reference the well-known fall of the great Atari, which began the Atari 2600 games market fiasco. This was a great piece of hardware destroyed by reams of shitty games on store shelves (see for yourself, look up ET for the 2600). The Nintendo NES that followed about 2 or 3 years later in 1985 (after most of the North American gaming industry had imploded) was well-known for its third-party licensing agreements which helped (while obviously not perfect) to ensure some quality games on store shelves. As a result, the NES was super successful and the gaming industry was reborn.
If Apple is to the Nintendo and the NES, what Microsoft is to that shit that was allowed to happen with 2600 (note, that I do think Atari was an innovator for having introducing home gaming to NA in the first place!), then I think we have an idea of what Apple's future might be if they decide to lock down their platforms. That is, there will enjoy probably another 10 or 15 years of success and astounding revenue, but they can definitely expect some tremendous and very unlikely competitors down the road.