The biggest buzz this year is about iCloud and how it will be a streaming iTunes service/locker like those already announced by Amazon and Google. The big difference is that Apple has been working to secure streaming agreements from the major music labels, while Amazon and Google pretty much gave up on doing so and launched their services without label approval or cooperation.
This difference frees Apple from the kind of legal battle with the labels and Recording Industry Association of America that Amazon and Google now likely face. More important, it will probably obviate the need for a service that is solely locker-based.
Both Amazon and Google require you to upload your existing music library. Without any license agreements, they have to do this because they can only share files that you already own. (Amazon will place a copy of new purchases into your locker automatically, however.) Most of us, however, have music libraries that are in the tens or hundreds of gigabytes in size. That's a lot to upload -- something that could take days or weeks to do, depending on your Internet connection.
With label approval, Apple can just use a list of music that you own and stream files that already exist on its iTunes servers. Only your iTunes database needs to be uploaded. The various iTunes database and XML files on my Mac total around 20MB. That's a much shorter upload, and Apple probably needs only the iTunes Music Library database and/or iTunes Music Library XML files. In fact, if you've turned on the iTunes Genius feature, Apple likely has all the data it needs to stream music from its servers.
Of course, that raises the question about music that didn't come from the iTunes Store -- songs that you ripped from your CD collection, acquired from other music stores, recorded yourself, or got from other legitimate sources. The labels probably won't let Apple stream those titles. Apple could let you upload them to a locker for streaming, or stream them directly from your Mac or PC using your home's Internet connection.
I'm guessing it'll be the latter, because I think the labels might object to the former and because a recent Apple patent essentially describes a system for streaming from Apple servers and your home computer.
That patent also includes a "partial sync" feature that indicates that iOS devices could gain the ability to sync some tracks to the device (for playback with no Internet connection) and stream the rest. That would be a great for iPod Touch or Wi-Fi iPad users.
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