I'm on vacation so I'll keep this short.
I don't get the idea of music locker services like the one Amazon just announced. If I'm going to stream music from the cloud, why should I continue to buy files and collect them? I've been a Rhapsody subscriber for something like 11 or 12 years and although it has taken a while to get used to, I vastly prefer subscription streaming services over file based music. I've just stared using rdio on my Android and on the web and I love it too. I've used Spotify and it is also excellent (once it is fully licensed in the US).
Locker services seem like they are designed to continue the physical model of collecting music and buying music when there is a new and better way – just subscribe to music dial tone and listen to whatever you want wherever you want.
I'm bearish on locker services and bullish on subscription streaming services.