I am a bit of a security wonk and strongly dislike guest accounts so one of the things I have researched since loading up Ubuntu 11.10 is how to disable the guest account available on the login screen. In the past, with GDM, all that had to be done is an uninstall of gdm-guest-session. With Ubuntu 11.10 switching to lightDM this has changed. To remove the guest login option you have to modify /etc/lightdm/lightdm.conf.
You can either reboot or restart the service.
sudo restart lightdm
Please note that restarting lightdm will end your session so do not do this with applications running. This will now remove the guest login as an option from the login screen. I hope this helps out anyone, who like me, is concerned about restricting access to their computer.