Thomas: that behaviour looks like a bug. Are all of those volumes mountable by the user? The drive mount applet is only meant to show icons for the mount points the user can mount.
Note also that the applet is using the exact same information for the list of drives as Nautilus is. If the applet is confusing, then wouldn’t Nautilus’s “Computer” window also be confusing?
To help debug things, I wrote a little program to dump all the data provided by GnomeVFSVolumeMonitor:
Does the output look sane for you? In particular, are any drives or volumes marked “user visible” that should not be?
The drive mount applet shows two icons on my thinkpad: a floppy drive (which I don’t have), and a CD drive (which is the only one I want).
I’m not sure how GNOME could figure out that the floppy drive doesn’t exist, since even the kernel thinks it is there.
Marius: do you happen to have an entry in /etc/fstab for the floppy drive mount point? If you remove it, Gnome will probably stop thinking you have a floppy drive.
The “Computer” window has text labels for all icons in it, making it substantially more navigable, although much more desktop-space-greedy.