Apple Corporation (formerly `Apple Computer Corporation') has struggled with the cloud in various endeavors such as MobileMe and iCloud, but it seems to me that Apple would do better to return to their original effort in the area of the iDisk.
Give everyone with an Apple device and iTunes ID webspace and a web page. Then Apple could offer HTML apps that would work across every platform and on every device. Provide a basic API that would allow Mac apps and iOS apps to save to and draw from the same storage pool the web page does. Provide a free level of storage and least out more storage as the user wants.
Don't try to be Facebook, don't try to be Twitter. But a Dropbox Apple could be.