On a fresh install of Kubuntu 13.10 beta2 with all updates (lightdm 1.8.0), lightdm seems to ignore the setting of both greeter-hide-users and greeter-show-manual-login in /etc/lightdm/lightdm.conf. In my case, this file looks like:
[SeatDefaults]
user-session=kde-plasma
greeter-session=lightdm-kde-greeter
greeter-hide-users=true
greeter-show-manual-login=true
allow-guest=false
With these settings, no user list should be displayed (which is corporate policy here) and a manual login should be displayed. Despite these settings, the user list is still displayed and no manual login is shown. Is looks as if lightdm silently ignores those settings, although the conf file is being read (see attached log). To make matters worse, the missing manual login means that noone can log in, as we are using NIS and NIS users are not displayed (see https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1012147).
For now, the only workaround for us is to install kdm and use that instead - that session manager just shows a manual login out-of-the-box.
WORKAROUND:
Creating a file /etc/lightdm/
[greeter]
theme-name=classic
gets lightdm to display a simple login where one can enter username and password. I think this theme should automatically be displayed if a user adds the configuration options mentioned above to the main config file.