First, the bad news: the busybox Amazon ships the Kindle with doesn't have telnetd compiled in.
And now for the good news: Linux ARM binaries work just fine. Like the nice static build of busybox for Android I had laying around.
As of about 2 hours ago, I was treated to this lovely sight:
# telnet 192.168.15.244 2323 Trying 192.168.15.244... Connected to 192.168.15.244. Escape character is '^]'. kindle login:
By now, the utility of USB networking to the Kindle should be clear to most readers