Graffiti is as ubiquitous as telephone poles in America's cities; it is as old as the earliest civilizations. The most public medium in the country today, graffiti can signal territory, love, or liberation. Ironically, graffiti is understood by only a fraction of those who encounter it. Usually read as a sign of urban decay and as a loss of control over the physical environment, graffiti has become one of the most potent cultural languages of our...