gdm-2.6.0.5-6

In the graphical gdmconfig, it would be handy to be able to turn on
more than one X server, to allow multiple simultaneous graphical
logins.  This allows users who are only familiar with the graphical
interface to use the machine without logging out another graphical
user who has wandered off.  (A relatively common situation at home or
in small offices.)  

This may help improve security, accountability, and privacy by
reducing the use of shared logins and making it more convenient to
have the screen-locking feature of xscreensaver enabled.

You can currently accomplish this by editing /etc/X11/gdm.conf by
hand.