Oh I don't know, I find them rather comforting. Graffiti is people bragging, lying, and generally giving each other a hard time (about giving each other hard something elses, for the most part). But look at the precise balance you need for graffiti to work: a society stable enough to have durable walls, and lax enough that people can write on them without fear of being, say, thrown in jail for 5 years. In my opinion, that's a damn good balance.