As an aside, the system would only need to back up a database of what movies, music, and video games you own, and not the actual content. If you ever needed to do a recovery, your record of ownership would allow you to download the content again for free...
...Obviously all the technology to make this happen already exists. It's a matter of getting the cost down, negotiating all of the various licenses, and building an interface that is easy to use.
Actually, on second thought, the lunar X-Prize is a much easier task.