Sam Ewen’s firm is called Interference, and that’s a pretty good way to describe what he does. In a digital age, Ewen’s form of guerrilla marketing manages to break through the media landscape with real-life events. For instance, in 2007, Interference caught the attention of jaded New Yorkers by offering free parking on behalf of Vespa, the scooter company. More recently, Interference set up a window display on behalf of GE Healthcare with terms like “cancer” and “death panels” that lit up whenever someone mentioned those words on Twitter. That effort promoted a “pop-up symposium” in New York last month about healthcare. Ewen is best known to people outside marketing for his 2007 stunt in Boston for Cartoon Network that made national news after police thought that electronic light boards waving middle fingers were actually bombs. Ewen discussed that incident plus the current state of guerrilla marketing.