Awesome video. I think we need to flood the airwaves with these sorts of demonstrations.
Question: Isn't the mkfs.ext3 step unnecessary? Because you then proceed to dd over a previously dumped block image from the PC file "Kindle" to /dev/sdb1 (aka /dev/mmcblk0 on the kindle side).
And the key to this unbricking is that you previously had the foresight to make a block-level backup of mmcblk0 that you could later use for recovery purposes right?