It would be hard to claim that graffiti is not art of some sort.  After
all, it is visual, it has color, form, line, and surface.  Some of it is
technically bad and some very good.  It has content -- and like much 20th
C. art it has impudence, arrogance, and in-your-face irreverence -- and any
half-eager critic could fill it with volumes of socio-cultural meanings.

It seems like discussions about graffiti as art get modulated with people's
outrage over graffiti as vandalism.  The vandalism part of it is
abhorrent, and if someone tagged my neighborhood I wouldn't care how
aesthetically competent or culturally valid it was, I'd get rid of it.
Anyone who does graffiti on someone else's property ought to be thrown in
jail.

On the other hand, I once asked a student who was known to be a graffiti
artist to do a piece in our student gallery.  He did, and I liked it.
Defacing public or private property is wrong, but it has nothing to do with
whether the art of grafitti is good or bad.  And the fact that certain
graffiti might be good art should not justify its perpetuation.
Discussions of art can be above the law, artists cannot.

Stephen Nowlin
Vice President
Director, Alyce de Roulet Williamson Gallery
Art Center College of Design
http://www.artcenter.edu/exhibit/williamson.html