Can Apple's iCloud rival Google and Amazon?

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Media captionWith the iCloud the data is stored in Apple's servers and can also be accessed wirelessly by phones, computers and tablets

So Apple has at last got into the cloud, with Steve Jobs unveiling the iCloud service at the company's Worldwide Developers Conference.

What will the iCloud mean for users - and does it really pose a threat to rival services from the likes of Google, Amazon and Spotify? I've been taking a look.