Legally speaking, this isn't such a stretch, is it?
This means my music would be uploaded into the cloud—hopefully to a service that would store it for free. Maybe that'd be Google. They could call it Gtunes.
If someone like Google were taking care of this (maybe I'm putting too much faith in them), the system could be indexed and shrunk by eliminating redundancies. For example, Abe owns Michael Bublé's "Crazy Love", so it's uploaded to his Gtunes. When I upload the same song, Gtunes realizes they're matching files and stores only one copy on the server. That way supporting a huge user base wouldn't be a huge deal—80GB libraries would overlap and significantly reduce the cloudspace required.
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I submitted this idea to Google Labs, and this was the reply:
Thanks for the note, Nate! A lot of us here are interested in music, but from a business perspective, it's veeeery tricky. But I'll pass your idea along to our Ideas forum.
-the Google Labs Guy