Also, I think there are other effective approaches in some circumstances. People (including "the kids"), locally (Toronto) and other places I've heard of, have been paid (not a super common thing, but it happens) to do actual artwork. There's a mural I consider quite well done, not too far from my place, that isn't getting defaced even though it's in a place where I would otherwise ordinarily expect strong temptation to "tagging" and other graffiti.