The Innovator's Dilemma guy also talks about integrated vs. modular architectures. By integrated, he means made in one elegant piece, meshing together just so; by modular he means you can mix-and-match (eg. from different suppliers, or to customize attributes easily), with clearly defined standard interfaces. Maybe it sounds like modular is always better; while it is more customizable and cheaper, integrated can always outperform it. Which one wins in a market depends on what that market most demands at that time, with respect to where the technology is at that moment. Is it fast enough? Does it have enough functions? Is it flexible enough? Is it cheap enough? Markets tend to move back and forth between them, as they evolve over a period of years.

For smartphones, performance is still an issue (and will be for 2-3 years I'd guess, by Moore's law), and so integrated platforms do the best job at this. This is Apple's forte - but they have limited time to make hay and get as firmly established as possible.

It's limited, because once the market's demand for performance is sated ("fast enough"), the market will base decisions on other issues - such as price. And that is not Apple's forte, nor does Apple want it to be. Thus, Apple already has the iPad lined up. After that, there'll be in another market at a stage where Apple's extraordinary ability to integrate can shine.

To be clear: Android is modular.