Movie trailers--those previews of coming attractions before the start of a feature film--are routinely praised and reviled by moviegoers and film critics alike: "They give away too much of the movie." "They're better than the films." "They only show the spectacular parts." "They lie." "They're the best part of going to the movies." But whether you love them or hate them, trailers always serve their purpose of offering free samples of a film to influence moviegoing decision-making. Indeed, with their inclusion on videotapes, DVDs, and on the Internet, trailers are more widely seen and...