We use to be pretty conservative with regards to the GTK+/GLib versions Xfce releases depend on. The target versions for Xfce 4.8 and Thunar 1.2 are GTK+ 2.14 and GLib 2.16. Unfortunately, the HAL based monitor in GVfs has a few major shortcomings.
gnome-mount hard-coded. It depends on gnome-keyring and gconfd and is not really an option for us.
GVfs versions before April 2009 are missing the
“mount-pre-unmount” signal and
G_FILE_MONITOR_EVENT_PRE_UNMOUNT events. These are pretty important in order to destroy resources that may block unmounting of volumes/mounts. So basically, all versions of GVfs that depend on GLib 2.16 are useless for us.