Is Apple’s success now a self-fulfilling prophecy? Or will the cloud break its grasp?

According to a Deutsche Bank report, Apple has built quite a content business on the backs of the iPhone and iPad. The typical iOS device user has sunk $100 into content on their devices, but more important than the sum of those purchases is the Apple envelope that encloses all of those apps, songs, games and e-books. iOS content can only be used on iOS devices, so the more money a customer invests in the iTunes App Store, the more likely they’ll remain an Apple customer as they buy new phones, tablets and even PCs in the future.

Apple already allows you to take your purchased apps with you via iTunes when upgrading from one iPhone to another. Though music and video content purchases on iTunes can be transferred to other platforms, the ease of content management in the iTunes universe provides an inevitable inertia to stick with Apple devices. As Apple’s iCloud services emerge those binds will become even tighter by automatically synching content and applications among devices using whatever network connection is available (CP: With iCloud Apple changes the definition of ‘cloud’ to fit own needs).

That grip is only likely to get stronger. According to Deutsche Bank, investment in content and apps on iOS grew from $40 per device in March of 2007 to the more than $100 by March of this year. Apple customers aren’t just spending more money in iTunes, they’re carrying over their previous purchases, compounding their investment in the platform. The numbers took a slight dip from September to March, but that likely reflects the huge inrush of new Apple iPhone 4 and iPad subscribers, which started their purchase meters at zero. Apple now has more than 200 million iOS devices in the market, and as the subscribers buy more books, music and apps and carry those purchases over to new iOS devices, their investment will rise well over $100. For customers who jumped on the Apple bandwagon early, adopting the original iPhone or the iPhone 3G, their total investment in iPhone content is probably several hundred dollars already.

Apple’s rise through the mobile ranks almost looks like a self-fulfilling prophesy. Though no one can fault Apple’s technology, design and innovative services, the huge stakes its customers now have in Apple’s products would imply Apple is turning these customers into Apple fanboys for life. So are these 220 million iPhone and iPad customers locked into their smartphone and tablet platforms for life?

Probably not. Even if app developers don’t start cross-licensing software to different platforms, content and even applications are becoming much more fluid. Music, video, e-books, documents and anything else that be streamed or saved as file is becoming network-based, while the apps themselves become mere clients to access that content. New services like Amazon’s Cloud Player and Google Music—even Apple’s iCloud--are spurring that transformation, but in truth types of services have been emerging for the last year.

Amazon doesn’t just sell e-Books through its Kindle reader. It has Kindle apps for all platforms that allow you to download and synchronize your reading between PCs, tablets and smartphones—including the iPhone and iPad. Even though customers have the iTunes bookstore available to them at a touch of a button, many iPad customers are foregoing it to buy their ebooks from Amazon where they can share it among all of their devices, not just the Apple ones.

Netflix is developing a similar system. Its rapidly growing movie streaming business is platform independent, working just as well on an iPhone, iPad or Apple TV as it does on the Xbox, dozens of DVD and BluRay players as well as the PC. And Google and Amazon moving music into the cloud is just the next step. Eventually we’ll see cloud-based gaming networks and virtual office setups running word processing and spreadsheet software—the virtual equivalent of Google Docs—all detached from specific platforms. We’re moving away from buying downloadable software and buying specific pieces of content to licensing software and subscribing to content. In such a model, nothing remains OS or ecosystem specific.

Apple has seen this coming, which is why it has implemented iCloud in its own unique way. Rather than created a true cloud computing and services platform, it’s using the ‘cloud’ more as a way to move and manage content between devices. The common theme to everything iCloud is the underlying applications, services and content are all Apple’s. Apple realizes it will have to have a cloud, so it created a private one for its customers.

It remains to be seen if customers prefer that private cloud spanning Apple platforms, or a broader cloud reaching out to multiple clouds spanning an array of Apple rivals.