When nautilus is started with the --no-desktop flag,
it should assume that it is used as a file manager,
and not a desktop manager. As such, it should not
mount devices except for browsing them; thus, if
media_automount_open is false, the devices should
not be automounted.
This is a spin-off from bug #570314, where nautilus'
automounting was interfering with KDE's automounting.
A substantial part of the problem was the lack of a
preference (in the preferences dialog) to control
automounting. There is a preference for "Browse media
when inserted" under "Media", but that only controls
media_automount_open.