It probably not a great idea to have people bind mount /dev from the livecd into their chroot since mount thinks it has open files no matter where its mounted.
*** Bug 124521 has been marked as a duplicate of this bug. ***
According to a recent discussion, bind mount of /dev is required. Please reopen if you can submit complete error message while following our installation instructions.
The problem I ran into was that I screwed up my partition table on a system I was installing over ssh (ie I couldn't reboot it). So, when I backed out of the chroot to re-partition everything, I couldn't unmount /dev from the chroot.
Handbook says to exit the chroot at first.