Real Uses For Tagging: "I've also been thinking a lot about graffiti. I think there's a lot to be learned from analysis of it, although I think it is only one form of offline public authoring. There must be a sociologist/anthropologist who's done a thesis on what graffiti means. I'll post another entry later this week with some graffiti examples."
I remember an interview with Chuck D in Wired, years ago, where he described hip-hop as hypertextual on the basis that it was constantly referential. Graffiti seems (to me) to be similar - even when it's not as explicit as this.