I'm using LXDM 0.4.1 and on the default configuration in the category [userlist] disable is set to 0 and whitelist and blacklist are unset. Now LXDM shows me some random users on a fresh Ubuntu 12.10 installation. They are syslog, usbmux and saned. My first thought was if I set disable to 1 and add my useraccount sworddragon to the whitelist I will see only this user. But I was wrong because setting disable to 1 will deactivate the whitelist.
I think this could be a little enhanced. At least it would be much better if LXDM wouldn't list anymore system users at default.