Amazon Video Downloads: One step forward, Two steps back

Amazon has released its video on demand service (as reported by New York Times). This offers a reasonable price ($1.99) for recent shows (e.g. the Burn Notice première, less than a week old, is available), touted as a "play anywhere" solution, allowing you to view it on your PC or Tivo. A purchase adds it to your "Amazon Media Library" and you can view it right away or at a later time.

The problem is that this service works only on Windows XP Service Pack 2 or Vista computers. Sure, that is a large segment of computer users, but why is this the case? Why limit the service like this? Even if I had a Windows-based computer, how do I know that I will have it a year from now when I want to re-watch some of my tv or movies? How do I know Amazon will continue to support other devices as they come out? I want to be able to watch the TV on my Nokia Internet Tablet or my phone when I am commuting. More importantly, I want to be at a friend's house and say "you haven't seen Aliens yet? Ever?! You need to watch it right now!" and log into my account so we can watch the movie at their place, instantly.

Until these services are at least as portable as a CD or an actual download, they will never be more than a novelty. The recording and movie studios complain about piracy all the time, but until they give people what they want, bit torrent and other file-sharing services will continue to be filled with copyright-infringing content.