There is a solution, which several companies already implement (Rdio and Spotify, at least). You can sync tracks to your device. I haven't used MOG or Rhapsody

There is a solution, which several companies already implement (Rdio and Spotify, at least). You can sync tracks to your device. I haven't used MOG or Rhapsody so I'm not sure if they do it as well (anyone?) but it seems like the obvious solution. It's the best of both worlds, as you can still stream if you want.