Here's what we know for certain about the art-world enigma named Banksy. "Banksy is NOT on Facebook, Twitter or represented by Steve Lazarides or any other commercial gallery." The source of that simple and direct statement is the artist's website. We also know that the artist has made a great number of stenciled graffiti paintings on walls in the U.K., North America, Europe, and the Middle East. In 2010, he released a film about his work...