At the moment Apple is using CDN providers like Akamai and Level 3 to deliver its content like apps, iTunes Video, software updates an more.
I’m hearing that part of Apple’s reasoning for building their own CDN is because of performance issues with iCloud, with Apple wanting to have more control over the QoS of content going to their devices. Apple already controls the hardware, the OS (iOS/OS X) as well as the iTunes/App store platforms. Right now they control the entire customer experience, except for the way content is delivered to their devices. Since Apple does not own the last mile they won’t be able to have complete control, but having their own CDN would give them more control and security than they have now. The next set of questions to ask is what type of technology Apple uses? Will they go the open source route and built it in a non-proprietary way, or keep it closed? Some will also wonder if Apple might make their CDN into a commercial offering, but that wouldn’t make any sense for their business, unless they had some kind of content subscription service akin to Netflix.
Apple has yet to confirm that they are working on their own Content Delivery Network, although it would be a good move for the company as it would give them greater control over their content.