When we tried Paranoid Debating at the Boston meetup a few years back, we often had the problem that the deceiver didn't know enough about the question to know which direction to mislead in. I think the game would work better if the deceiver were simply trying to bias the group in a particular direction rather than make the group wrong. I think that's also a closer approximation to real life - plenty of people want to sell you their product and don't know or care which option is best. Not many just want you to buy the wrong product.