A wall is a very big weapon. It's one of the nastiest things you can hit someone with.
Imagine a city where graffiti wasn't illegal, a city where everybody could draw whatever they liked. Where every street was awash with a million colours and little phrases. Where standing at a bus stop was never boring. A city that felt like a party where everyone was invited, not just the estate agents and barons of big business. Imagine a city like that and stop leaning against the wall - it's wet.
Although you might have to creep about at night and lie to your mum it’s actually one of the more honest art forms available. There is no elitism or hype, it exhibits on the best walls a town has to offer and nobody is put off by the price of admission.
Graffiti 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?