Does the iPhone's Closed Nature Foster Innovation?

aussersterne writes: The heated debate over Apple's "walled garden" has ranged for years now, only growing more intense with the rise of iPhone apps and the recent release of the iPad. Contrary to conventional wisdom, however, some are suggesting that Apple's particular approach to closedness has actually been a boon for innovation and egalitarianism in ways that few had previously thought possible. In a recent NYT article, Steven Johnson says, "I’ve long considered myself a believer in this gospel and have probably written a hundred pages of book chapters, essays and blog posts spreading the word. Believing in open platforms is not simple techno-utopianism. Open platforms come with undeniable costs. The Web is rife with pornography and vitriol for the very same reasons it’s so consistently ingenious. It’s not that the Web is perfect, by any means, but as an engine of innovation and democratization, its supremacy has been undeniable. Over the last two years, however, that story has grown far more complicated, thanks to the runaway success of the iPhone (and now iPad) developers platform — known as the App Store to consumers." Can a walled garden, as Johnson suggests, actually give rise to a "rainforest" if executed in Apple-like ways?