Wulf, I'd love to see that article if you ever find the link to it. Some web browsers retain the history of the sites you've visited recently (hint-hint).
To me, this looks like a rigged shot. A great example of this can be found
here (scroll to the bottom to find out how it was done). Only issue is that a portion of the car isn't in the photo to hide the rig. I'm still trying to learn more about rigging, getting the whole car in the photo, and the post processing work required, but most who've been successful at this are tight lipped about it.
I'd rule out panning due to the direction of travel and the sharpness of the car throughout the photo.
I still need more practice doing "
rolling shots". I had a friend drive his Exige in a large circle around my car traveling in a tighter circle (~5-10mph). We synced up and I had my camera mounted to the outside of my windshield, prefocused in Aperture priority mode. Used remote shutter by sticking my hand out of sunroof. Seems the sweet spot for shutter speed is around 1/10 to 1/4 of a second for what I've attempted so far. Anything faster and there isn't enough motion blur; slower can be more artistic, but also more subject blurring (see 2nd photo below).
