I've recently been giving a lot of thought to the question of graffiti, public art, and street art. It's a preoccupation of mine that's bubbled up through a number of recent encounters and experiences. For starters, we live in a quasi-urban neighborhood. There's a lot of hapless and ham-handed tagging in our area along with a few pieces that are slightly more advanced. The neighborhood fairly insures that my encounters with graffiti will be an everyday occurrence.
Add to that my fine arts background, a fanboy's love of "Exit Through the Gift Shop", and a propensity to frequent message boards where graffiti is a recurring topic, and you've got a recipe for some extensive consideration. I'm still more or less a dilettante on the subject, but I find my level of interest in the genre has increased as street art has evolved. While traditional graffiti and tags still bore me to death, I'm more than happy to enjoy those works that have progressed beyond this very narrow style. At it's best I've found street art to be funny, provocative, inventive, and human.
Now I'm not suggesting that this expressive component mitigates or excuses any criminal responsibility. It doesn't. I'm also not suggesting that the expressive component always has value. It doesn't. I'm simply suggesting that because graffiti and street art are forms of visual expression, they can be discussed on those terms.
While it's reasonable (and right) to point out that illegal street art is costly and wrong, we should understand too that the visual, formal, and expressive elements of a work aren't nullified simply because it’s illegal. Those elements exist and are there for us consider whether we're looking at something legal or not. In fact, according to McLuhan's assertion that "the medium is the message", it could be argued that street art's illicit nature is actually part of the expression. It's a way of saying (on top of whatever else might be conveyed), "I don't much care about your rules".