While we're at it why not put in WIFI and not even HAVE to use a cable? Would eliminate a LOT of the cost to Amazon for Whispernet.
I seem to recall a post about RE-enabling USB networking so that the Kindle CAN receive updates via a connected PC. I think it was a boon to people outside the US using a non international Kindle. I can't find it though.
EDIT: It's here and DX only:
http://www.flixxy.com/worlds-luckies...-inspector.htm