Ubuntu 9.10 loses some security via login screen

[Tom V]

Previous versions of Ubuntu always prompted users for BOTH a user name and password. Now it appears that the or a user name is loaded at startup and if the user agrees with the selection then the enter key is pressed and a password in entered. This makes Karmic slightly less secure than previous versions which required the user to enter both at the login screen. If Linux is to continue to advertise itself as being a more secure operating system then the convenience of having the OS preselect my user name at startup should give way to the older method of having the user required to supply both.
Is there a way to disable this auto selecting of a user?

ProblemType: Bug
Architecture: amd64
Date: Sun Nov 29 11:23:40 2009
DistroRelease: Ubuntu 9.10
ExecutablePath: /usr/bin/yelp
NonfreeKernelModules: nvidia
Package: yelp 2.28.0-0ubuntu2
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-15.50-generic
SourcePackage: yelp
Uname: Linux 2.6.31-15-generic x86_64

[BrianS (brians200)]

sudo -u gdm gconftool-2 --type bool --set /apps/gdm/simple-greeter/disable_user_list 'true'

that will make it to where you have to type user name and password

[Phil Buckler (buck2825)]

sudo -u gdm gconftool-2 --type bool --set /apps/gdm/simple-greeter/disable_user_list 'true'

returns

Error setting value: Can't overwrite existing read-only value: Value for `/apps/gdm/simple-greeter/disable_user_list' set in a read-only source at the front of your configuration path