This is curious: InfiniteApple is saying they've confirmed that iCloud is powered by Microsoft's Azure, at least for the moment.

The folks at InfiniteApple sent files to and from iPhones with iOS 5 beta installed and monitored the traffic. They concluded that iCloud doesn't actually store anything. Instead, it simply "manages links" to content stored elsewhere—in this case, Microsoft's Azure services. iCloud's still in beta, so this may be a temporary solution. Still, how great would it be if the defining feature of Apple's year turns out to be powered by Microsoft? [InfiniteApple via ZDnet]