I wrote up a post on why the Samsung extreme Sheep LED Art was fake, so I figure I need to write up this one on why the Honda Insight LED video is (mostly) real. Here's the video:
(Thanks Laughing Squid)
Of course, there is a good bit of post production work on this spot, but I do think they shot something in the desert that would have looked pretty cool to the naked eye (at least a naked eye in a crane). One point, though, this can't be "one of the world's largest LED screens", since LED stands for Light Emitting Diode, and the Insight uses, "Projector-beam halogen headlights".
Honda also produced a making of video, which while short on technical details does have some important info if you know what to look for:
A couple key points here:
At about 2:07 you can see what looks like a standard car headlight mounted in a frame, so they didn't need to have hundreds of cars out in the desert to get the end effect (finding that many of a car brand new to the market would have been the hardest part of the whole gig). You can see these fake cars from a different angle at about 2:36.
At about 3:15, after some ad agency guy breathlessly says, "there was no known way to do this" (which is just silly--it's just a console with a whole lot of dimmers, just like Pulse Park, which I wrote up here), they introduce Tim Dunn, who is a real lighting designer, apparently associated with Gearhouse in South Africa.
At 2:55, you can see Mr. Dunn in front of a GrandMA lighting console. These are very common, we are using one right now on the Tribeca Film Festival Drive In, and we're buying one at the school. So there certainly was a "known way" to do this, especially using pixel mapping software.
Still, it's a very cool idea!