Comment 89 for bug 12893

The fix from upstream is that the user is prompted to emtpy the trash when the drive is unmounted. This fix is in Karmic, but a big problem is that this dialog is not triggered when ejecting a drive in Nautilus, only when unmounting.

In Nautilus "ejecting" is the default action, "unmounting" is only accessible through a context menu. Most users therefore probably never encounter this dialog. The obvious fix (to me) would be to also trigger the dialog on eject, not only on unmount (Although I really don't know the difference between these two actions).