I like trailers but they are not all created equal. The longest trailer, released close to the release of a movie, is usually spoiler ridden. It will contain shots from every important scene, each action sequence/set piece, the crucial plot twist moment, and all the good effects shots and props. They take much of the awe and surprise out of seeing a movie.<p>The 30-60 second teaser trailers seem to be much better. They still get you interested, but don't try to actually hide things, and leave you wanting more.