When booting a live USB key with the latest live-initramfs, no user is created upon boot. Upon investigation it seems that the 10adduser script doesn’t populate the debconf database in /root/var/cache/debconf at all. Therefore user-setup fails and nothing is done.
Welcome aboard... see http://lists.debian.org/debian-live/2010/05/msg00108.html
Jiri Palecek