Agreed. I don't use a Kindle, but having a (optional, configurable) "Rate this book?" prompt when removing a book from my in-progress shelf would be very handy.
It's even more frustrating than that, currently, because when you finish a Kindle book, it asks if you want to tweet about it or post it on Facebook. I don't, but I very much want to post my rating of it to Goodreads, and that isn't currently an option.
This fixes a big hole that a lot of people (at least, a lot of people on Goodreads) have been clamoring for.
Considering Amazon already has a review section for each book it sells, this seems like it was already a missed opportunity. It's great they're probably not going to kill the service, but it seems like it'd have made sense to have more tightly integrated their own reviews a long time ago.
