When urban spaces become the medium for expression, protest, criticism, and defiance, the audience is limitless. Pedestrians and bystanders of all ages and ideologies become spectators of demonstrations that walk the line between art and activism and transform the city's streets, walls, and sidewalks into canvases for diffusing ideas on a massive scale. Banksy once said that "a wall is a very big weapon. It's one of the nastiest things you can hit someone with." This call to arms has rung true for many as they take to the streets in a bid to make themselves heard.