Comment 7 for bug 944041

Integration into Active Directory requires an authorized administrator and some PAM and samba configurations.
Once the workstation is joined to a domain, in oneiric (with lightdm) and previously (with gdm), active directory users could login by entering username and password. The presence of the 'Other username ...' dialog is essential here, unless the workstation is used mainly by a single user, which can be listed by lightdm by adding it to /etc/passwd.
I think that a good solutions could be to leave off that dialog in the default configuration, but add an option in lightdm.conf to restore it without hiding local users (as it is now).