All those Banksy pieces popping up around the Sundance Film Festival are promoting Exit Through the Gift Shop—which is either a documentary or a mocumentary or a big stunt about Banksy or some other dude. Look, another picture!
UPDATE: A bit of clarity from Brooks Barnes:
"Exit Through the Gift Shop" is about an eccentric French shop keeper and amateur film maker who was so obsessed with Banksy that he wanted to make a documentary about him. But the British-born Banksy turned the tables and made a film about the effort to film him.