question about Unmount/Eject on removable media menus

["Peter F. Patel-Schneider" <pfps verizon net>]

Hi:

I'm confused as to the actual difference between "Unmount Volume" and 
"Eject Volume" for removable media.

I think I know how they might work:
- Eject Volume would be for media in devices that have an actual eject 
action (like CDs and floppies)
    - it would first do an unmount and then perform the eject (if 
possible - some media eject might not
      be under software control)
- Unmount Volume would be for other sorts of media

However this does not appear to be what is happening.

First, there is the warning in the Nautilus user documentation
http://library.gnome.org/users/user-guide/stable/gosnautilus-464.html.en 
in "To Eject Media" that says

You must unmount removable media before ejecting. Do not remove a USB 
flash drive before you unmount the flash drive. If you do not unmount 
the media first you might lose data.

Second, the "Eject Volume" entry seems to show up almost at random.  It 
shows up for some of my USB keys, but not others; it shows up for a 
PCMCIA to CF adapter.

Does anyone know what the situation is supposed to be?  Is it that 
Nautilus just picks up on some property of the media provided by some 
underlying layer?

Peter F. Patel-Schneider