He's right:i don't even see how it could be mounted on the same car?! :AF:
<a href="http://www.flickr.com/photos/radiantmark/4613026557/" title="Original unedited rig photo by Mark Jardine, on Flickr"><img src="http://farm4.static.flickr.com/3411/4613026557_02bf12b12f_o.jpg" width="800" height="533" alt="Original unedited rig photo" /></a>
The hardest part is removing the rig from the photo. This is how all all the very sharp moving car photos are done for magazines.
Here's a pretty decent writeup on it: http://www.diyphotography.net/take-cool-car-photos-with-a-diy-specialized-car-rig
I bought pretty much the same hardware from that article.