I was just listening to an Episode of the Nerdist podcast featuring Aziz Ansari today and he talked about the issue of people taking pictures or filming his live material and leaking it to the public. He said he had no issue with people recording material that is already public, but that it really stinks when new material is leaked because it waters down the humor for future attendees of his shows. To combat this, at the beginning of his shows, he asks everyone to take out their phones/cameras and stands there while they take pictures of him. Then he nicely asks them to not use their phones/cameras during the rest of the show. Obviously this doesn't stop everyone but I think it's a pretty low-cost, high reward option.