Here is what /etc/lightdm/lightdm.conf looks like to remove the list of users, require users to type in their usernames to log-in, and not allow guest or remote log-ins to Ubuntu.
UPDATE: On Ubuntu 13.10 the lightdm.conf file might need to be created.
UPDATE: On Ubuntu 14.04 the lightdm.conf file might need to be created.
[SeatDefaults]
allow-guest=false
greeter-show-manual-login=true
greeter-hide-users=true
show-remote-login=false
