Comment 3 for bug 8159

Shutting down would make sense, if it was done properly. However, just calling
shutdown isn't a good way of closing down a system if it's being used as an X
workstation. At the very least it needs to end all gnome sessions cleanly so
that they are saved and will be restored at next boot; or else every time
someone hits their power button by accident they're going to shoot someone. You
can see how this is done for KDE in the acpi script, but I don't know of any way
to do this properly for gnome.