Heres a ad-firm's self promo in the UK that markets reverse graffiti by cleaning soot and filth off of walls.

Does anyone remember someone tagging "AMOK" all over Manhattan curbs circa 01/02?
Exit Through The Gift Shop thoughts: I guess I'll make it spoiler :/
[spoiler]Kitsch can only be so ironic before even the dumbest of people see through it, and yet 'Mr. Brainwash' dupes thousands of L.A. hipster wannabies into spending thousands of dollars on clichéd reinterpretations of Warhol.
My interpretation of Mr. Brainwash was that he was just some guy that Banksy was hanging around with and decided it would be funny to make him into a trendy art star by basically making cheap ripoff art and hawking it to the bandwagoning masses. I believe the existence Mr. Brainwash himself was Banksy's creation meant to be a commentary on the art world and art's consumers.
[/spoiler]