Further investigation resulted in this screen shot -
Interesting to see Amazon offering this, but what about paying a slight upgrade fee to give me Kindle access to existing purchases? I've blogged about this idea before. Either way this is a great scalable way to to generate incremental revenue with almost no physical distribution costs. I wonder what the economics are with the publishers.
I'm sure there are some rights issues, but the reality is that with this solution or Kindle upgrades there is still the potential that I have sold the book on the secondary market. The only challenge is that most books depreciate rapidly after purchase.