Brandalism Any advertisement in public space that gives you no choice whether you see it or not is yours. It belongs to you. It's yours to take, rearrange and re-use. Asking for permission is like asking to keep a rock someone just threw at your head.
BanksyGraffiti ultimately wins out over proper art because it becomes part of your city, it' s a tool; "I'll meet you in that pub, you know, the one opposite that wall with a picture of a monkey holding a chainsaw". I mean, how much more useful can a painting be than that?
Banksy