Ad regulations are mainly aimed at safety and appearance from the street. I doubt there are many regulations about ads lying flat on one's roof. As for ad ban

Ad regulations are mainly aimed at safety and appearance from the street. I doubt there are many regulations about ads lying flat on one's roof. As for ad banner vs. QR code, I think the QR code wins, pixel-for-pixel. If you look at that picture in the article, replacing the QR code with some sort of ad at the same size (or even just text) would require the viewer to have to zoom in further to make it out.