Graffiti: Where to Draw the Line

Reading Gregory Snyder’s Grafitti Lives was an eye-opening experience for me. Though I am generally against the government being able to dictate what a person can and cannot do, I had always somehow held this notion that graffiti artists were no more than low-class criminals without respect for private property. Snyder’s book caused me to question this conception, and left me wondering where the line is concerning what does and does not constitute graffiti.
It was his discussion of pieces in his chapter “A Brief History of Graffiti Writing” that really led me to this question. In this chapter, Snyder talks at length about the three different types of graffiti: the piece, the throw up, and the tag. Though he generalizes what constitutes each type of graffiti, the chapter still left me unclear as to where the line is drawn between each. For example, when does a work of graffiti stop being a mere tag and constitute a piece.
Though this distinction might be easier to define, the question that really bothers me is this: what is the difference between a graffiti piece and a mural? Is it the legality of one as opposed to the vandalism of the other? Furthermore, just because something is not sanctioned, does this make it not art?
Of course, these are difficult questions to tackle. In New York City alone, there are some pieces on the streets that would rival some of the greater works of art found in museums – and it is indisputable that most of these works of graffiti can be classified as art. Yet as a matter of consistency, I’m still concerned where graffiti stops and legitimate art begins.
The best online definition I could find of graffiti (actually, graffito, which is the singular version of graffiti) was: “A drawing or inscription made on a wall or other surface, usually so as to be seen by the public” (thanks dictionary.com). Yet this is still insufficient to answer my question, for a mural or other legitimized work could fall into this category.
A second definition, also courtesy of dictionary.com, was this: “markings, as initials, slogans, or drawings, written, spray-painted, or sketched on a sidewalk, wall of a building or public restroom, or the like : These graffiti are evidence of the neighborhood's decline.” Though this definition is very similar to the first, and furthermore, does not differentiate graffiti from other art forms, I found it interesting by virtue of its sample sentence. Though the definition does not contain any of the negative implications often associated with graffiti, the sentence conforms to all graffiti stereotypes. Therefore, I would contend, that graffiti is not outwardly different from other art forms, but is differentiated merely by its connotations which link it back to the underground subculture from which it was born.