I have known one. It was this guy I met at a reddit meetup who I hang out with a couple of times after the meetup. He was really into sneakers and he said his life changed when someone on a train gave him the movie, Loose Change which opened his eyes to the 9/11 truth movement and conspiracy. On facebook, I always see him posting conspiracy theories but that Loose Change story was the only time I heard him talking about conspiracies in real life. He said he went from a republician and believing in the war in Iraq to a conspiracy theorist after seeing Loose Change. That's the only person I can think of that I know in real life that believes in conspiracy.