According to an article on The Register, Apple’s iCloud service is rumored to run jointly on Amazon’s AWS and Microsoft’s Azure. I cannot help but wonder if Apple is relying on established, reliable vendors for the initial iCloud launch, and later migrating the service over to their data center in North Carolina when they feel it is ready.
9to5Mac has posted two internal Apple "First Look" documents aimed at arming Apple Store employees with talking points to help sell iOS 5 and iCloud. Although it is unlikely that employees would need to sell these services independently, seeing as they are bundled for free with an iOS device, they are enhancements that could help sell new iOS devices, as well as keep existing iOS users from switching to competing platforms. The two images are available to view here once you click "Read More..." below.