Comment 41 for bug 404185

Also:
I can confirm that sudo eject /dev/sdb works as expected.
With palimpsest, unmounting the partition and then using the _third_ "eject" button works.
However, unmounting the partition and the using the _fourth_ "Detach device from system and power off" button, results in exactly that happening and the device won't return until reboot (as happens when you press the button in Nautilus).
-Stuart