Just in case you were wondering, the Amazon Kindle can charge over USB. I know I wondered, before I bought mine, and lots of people have asked me since I got it. So here’s the proof – that little orange LED next to the USB cable is the charge indicator light. It’s plugged in to my MacBook Pro. It’s probably slower than charging from the brick, but at least it works.
I really like this because it means when I travel, I can go with one less proprietary power brick/charger cable, since a lot of my gadgets can charge from a USB power brick (and many also share the same standard mini USB cable, like the one the Kindle uses).
Posting for posterity, Google, and future reference.