Hidden behind the curtains at this year's Apple Worldwide Developer Conference, iCloud was really pulling all the levers. It reminds me of Woody Allen's eponymous character in the film Zelig, who appears in the background of virtually every important event in the 20th Century.
Like Zelig, iCloud is always there, always in the background of everything that Apple is doing now. (Although, unlike Zelig, iCloud doesn't actually change its appearance and identity depending on the situation. Even Apple hasn't mastered that particular technology yet.)
The aim is simple, and Apple is overt about it: iCloud is going to be the default place that apps store files, and they're going to be accessible from iOS and OS X. The idea of stuff stored locally is gradually going to go away. You see this throughout the iPhone 5 and iOS 6.
At present with iTunes In The Cloud, for example, if you tap on a song that's not available locally, it will be downloaded as you listen and kept on your device. With iOS 6, iTunes In The Cloud songs can stream to your iOS 6 devices without being downloaded. The cloud is the storage - all that happens locally is that it's cached, behind the scenes.
But there's more to iCloud now than saving you space by storing your documents and music elsewhere. The idea is to give developers the tools to let you use your apps on any device and pick up where you left off, no matter what platform you're using.
Syncing between your devices
Start a game on your iPhone on the tube, and pick it up on your iPad when you get home, from exactly the same spot in the game. Listen to a podcast on your iPad, put that down, and pick up from the same point in the show on your iPhone. iCloud is intended to be the invisible magic that glues your iPhone, iPad and Mac (if you use one) together.
Of course, when you have clouds, you also have turbulence, and sometimes a little rain, too. So far, developers have been relatively slow to pick up on iCloud, because some of the core features have lacked the kind of responsiveness and flexibility they need to create great experiences. Apple's done some work to address this in iOS 6, but there's a lot still to be done.
On the user side, iCloud still feels a little hit-or-miss in places: sometimes, for example, Pages documents end up in the cloud instantly. At other times, they don't. And when you're relying on the cloud for storage, it needs to be totally reliable.
There are also the issues that Apple can't control, such as the need for a speedy and reliable net connection available constantly - still not exactly the norm in many countries.
But make no mistake: iCloud is the most important thing that's happening on iOS at the moment. It's the heart of what Apple thinks is the future of virtually every product it does. You're going to be hearing a whole lot more about it over the next year, as Apple pushes its own products further and developers adopt its features more widely.