Graffiti/Not Graffiti

At what point does marking property that is not yours become graffiti? When it's detructive? When you are using paint or a marker? In the case of a British artist that goes by the name of "Moose", he is not actually marking the surfaces he uses, but creates his art by removing the dirt and dust from the surfaces. Apparently British authorities are having a hard time trying to decide what to do about Moose's art. He says he got the idea when he saw people's names written on a dusty tunnel wall, and thought he would step-it-up a level. His only tools required are a shoe brush and water.

See more work here.
[via: ComputerLove]