Comment 7 for bug 23293

I was just looking for the same thing; this is still he behavior on Hardy, and it's counter-intuitive.

When one unmounts a device, one expects it to be ejected and off the system, not to launch a new window. It creates clutter and can be confusing to new users.

There must be an easy way to do this, but I don't see any relevant options in man umount (which means nothing, because I'm not all that certain what the options do).