iCloud is Apple’s online “cloud” offering of sync, storage, email, and more. It is the successor of MobileMe and thus also the successor to the infamous .Mac, but it’s more than just a new name — it’s a new game for Apple. This time around Apple [knows how important iCloud](http://gigaom.com/apple/for-apple-icloud-is-just-the-beginning/) is to the success of iOS and OS X.

A [report from the Wall Street Journal](http://online.wsj.com/article/SB10001424052702304371504577404180417927436.html?mod=WSJ_latestheadlines) (subscription required) talks about rumored upgrades to iCloud — all of which make sense if you really think about how important iCloud is to Apple. iCloud is essentially the sanity glue for all iOS+Mac users out there — of which there are millions.

iOS and OS X can survive on their own without iCloud — that much we know from history. However, at this point, iOS and Mac OS X cannot survive *together* without iCloud — because without iCloud the alternative is Exchange or iTunes, both of which are cumbersome at best and downright aggravating most of the time.

Apple products are often described as something that ‘just works’ and while you may disagree with that, it’s hard to disagree with the notion that a large part of the ’just works’ ideology is: seamless integration of hardware and software.

That’s easy with laptops, that’s easy with mobile, but it’s hard if you want the seamless integration *between* two different (or same for that matter) devices. This is why most of us nerds love Dropbox sync, because Dropbox makes it easier to work on two Macs in a back and forth scenario. This is what iCloud is trying to solve between not only Macs, but Macs and iOS.

This is why iCloud success is crucial to Apple.

This is a problem Microsoft will also need to solve, but by the very nature of Google, it’s not a problem that Google need solve — because they have solved it as much as they want to: use Google products only on the web, we don’t do desktop.

It only makes sense then that iCloud keeps expanding, because the more tasks it takes on between devices, the happier users will be and Apple will also strengthen two key areas:

1. Bullet point checklists when compared with competitors.
2. Platform lock-in. If all your data lives in iCloud and not Microsoft or Google, well you are far less likely to undertake such a large data migration.

I would be surprised if iCloud wasn’t a very large part of WWDC this year. Apple will be putting the finishing touches on iCloud’s integration with iOS and Mac OS X, but they will also need developers to give widespread adoption to its use for the service to catch on.

This should scare Microsoft and Google, but more than that I think it should scare Dropbox. As much as I love Dropbox, iCloud is easier.

A widely adopted, seamless, fast, robust iCloud is the greatest threat to Apple’s competitors — and this time around I think Apple knows it.