Movie Marketing: The Sneak Preview

According to Company Town, the upcoming Tom Cruise flick, "Knight and Day" is expected to have less than stellar numbers at the box office. In order to make sure that does not happen, FOX issued sneak previews before the opening weekend. According to the article, Sneak Previews can be risky in the web 2.0 era. If the audiences do not feel that the film is excellent, they will be tweeting away and there goes any hopes FOX might have of a box office hit. I'd like to ask what you guys think of the process of sneak previewing. Can you think of any examples that you thought were great films and perhaps some that were less than stellar. Since they need all the help they can get I also posted the trailer, check it out!!