Consider the types of billboards that we most often see along the highway. They encourage us to pollute our bodies with unhealthy food, to pollute our minds with shallow amusements and to pollute our Earth by wasting resources and indulging in luxuries. The two billboards I photographed below are all-too-representative of what I've read along highways.

Yes, there are also billboards for public services as well as billboards for useful and reasonable products. What concerns me, though, is that most billboards carry unhealthy messages. There are so many unhealthy billboards out there that unhealthy activities seem to be norm. It's booze, gambling and conspicuous consumption all the way down the highway. What effect might this have on us? It reminds me of James Q. Wilson's broken window theory of crime: