John Hering wants to show me something. We're standing at a busy intersection in San Francisco's North Beach neighborhood; he pauses, takes off his black Tom Ford sunglasses, and points to the one-story-tall graffiti art on the side of a building. Next to a boy wearing a gas mask, the tag line reads: "If at first you don't succeed -- call an airstrike." A probable criticism of America's military, the work is one of several in the city by the enigmatic British street artist Banksy. "What really appeals to me is his willingness to leverage different mediums in incredibly creative ways to communicate a message that causes the viewer to truly think and ask questions," Hering says later.