Paramount Pictures will, that's who.

The studio has released a trailer for its micro-indie horror flick Paranormal Activity--made for a reported $11,000--and the footage focuses less on the film itself than on a test audience's reaction to it: 

I have no idea what kind of legal waivers (if any) the members of the audience may have had to sign, but I confess I'm a bit uncomfortable with this. However irritating it may be, I think the use of night-vision cameras in theaters to prevent movie piracy is essentially legitimate. Filming moviegoers in the dark in order to make them marketing pawns is another matter altogether.