I manually mount a remote file system (NFS; mounted on /mnt/cone).
I mount it from my personal account (i.e., NOT as root), using:
mount /mnt/cone .  My /etc/fstab allows user mounts.
The desktop detects this mount, and corretly places an icon called ``cone''.

However, at some times I receive multiple mounts of the same directory.
I suspect this happens when I logout and login again.  The mount is
not umounted on exit, but is re-mounted on login.  I don't really know
how this is possible, but the fact is that several umounts as root are
required to cancel all duplicate mounts.  After each umount, I check (ls -l)
the directory /mnt/cone, but only after the last umount is it empty.
The number of umounts required matches the number of icons on the desktop.
In addition, /etc/mtab contains multiple lines (again, the same number)
referring to /mnt/cone.

This occurs on another NFS directory I use (/mnt/retina) as well.