Later this week several Hollywood-related companies will announce a new digital media distribution system that's suppose to ignite digital downloads of movies (and possible other digital content). They call it DECE (Digital Entertainment Content Ecosystem). The key-feature being 'portability'.
This time a name without 'protection' or 'rights' in its name, but the result is much the same.
In the 'old' days DRM was implemented by protecting the resource with a key, and if you had the proper 'key' on your device the content was playable. Downside was that playback was mainly limited to only one device, or it was OS/player dependent (Windows -> Windows Media Player, or Apple iTunes, OSX -> Itunes).
If you wanted it to play on another device you had a problem, since you lacked the proper key to 'unlock' the digital content. Thankfully Apple has lot's of DRM-free mp3's in it's iTunes store, but not everything (like the movies / TV Shows) is DRM free, or watchable on lots of devices.