The vision of iCloud on the iOS and Mac platform
With the release of Apple's latest OSX operating system, Mountain Lion, the successor of Lion, one of the main noticeable features is the push towards the iCloud, within the operating system, to eventually have all apps storing documents and data on the iCloud, rather than on the macbook's internal file system. Now this has no doubt caused a lot of controversy, and perhaps will even have it's teething problems, but I look at it as a glimpse of what the future aims and means are. With the addition of the Apple Store in Snow Leopard, we started to purchase our mac apps from the online store, similar to how we do it on the iOS platform.
For the laptops (and indeed iOS has already had a bit of a head start, but with the same end-game), the idea is that all your personalised data, documents, game data, app settings etc will all be stored on the iCloud, so if you either upgrade your machine, loose your laptop or need to have it replaced by an Apple Genius, you can restore all your data immediately.
Now, the data is separated, or de-coupled from your actual application installations, which you hopefully would be able to get restored automatically from the App store, prior to the machine downloading and syncing your personal data from the iCloud. This is the aim of also the iOS platform, where your personal data should be backed up in the iCloud, but you would be able to create complete mirror backups of your device and its data on the iCloud already. For practical reasons, you shouldn't have to backup 256GB or 500GB of your laptop on the iCloud together, so rather than do that, Apple stores your personal data and app data, whilst the apps themselves are recoverable from the App Store.
That is definitely the vision I see Apple has having, and something I hope programmers start to prepare for.