[1] http://www.macrumors.com/2011/05/26/some-icloud-music-servic...
[1] http://www.macrumors.com/2011/05/26/some-icloud-music-servic...
If that's not the scenario, than what is? You can only stream songs newly purchased over iTunes and only iTunes?
I think wmf might be onto it. It could be a subscription thing. But as someone highly rated noted above, this whole iCloud thing might just be the developer's platform at this point in time (it is WWDC, after all), and the music stuff comes later in the fall with the iPod cycle.
This is how I see it too. Customers with smaller collections (i.e. the majority) will have higher margins, and effectively subsidise those with larger (and therefore with larger royalty payouts) collections.
Works similarly to the way ISP's do: users who use say, 20GB of a 60GB cap are more profitable than a user who uses 145GB of a 150GB. Bandwidth costs are small, but on a large scale, it works.