Or, when it comes to Apple, or Amazon, or Barnes & Noble and others, they already know what you've paid for. Those retailers should be able to review your purchase history over some span of time and just automatically provide you with the digital equivalent.

The service from Walmart for scanning the movies you already own, and the move by Apple to make new movie purchases available to iOS devices are both steps in the right direction. We just need to continue down that path and find ways that apply to both movies and books, and aren't tied to Vudu, or only functional with iOS devices.