Is urban graffiti a force for good or evil?

Ban it, legalise it, put it behind glass ... no matter what city councils do, graffiti remains the scapegoat for all manner of urban ills, from burglary on one extreme to gentrification on the other. But it may have another effect on cities entirely
In the spring of 2008, the Tate Modern opened the world’s first major public museum display of graffiti and street art, inviting six international artists to decorate its facade with enormous, eye-catching murals.
Meanwhile, just down the riverba