One of the first things I noticed upon moving to Houston was the preponderance of billboards--they're everywhere. They're so thick along highways like I-45 that it's like the street has been wallpapered with advertisements for lap-band surgery and radio stations. This was the only picutre I could find that even comes close to approximating the sheer number of billboards that cover the horizon in a way I have never before seen.
In fact, there's even a group dedicated to eradicating the problem--the Houston Quality of Life Coalition (from whom I borrowed the image). I wish them luck, because, speaking as someone who has driven along the Pacific Coast Highway (down the coast of California) and I-70 (through the Rocky Mountains), this mess is fugly.