astroengine writes with an amusing piece in Discovery. From the article: "In a study carried out by NASA and Pennsylvania State University scientists, several intelligent extraterrestrial encounter scenarios are examined. One of the scenarios is a sci-fi favorite: what if we encounter an alien race hellbent on destroying us? However, there's a twist. This isn't mindless thuggery on behalf of the aliens, and they're not killing us to get at our natural resources; they have a cause. They want to exterminate us for the greater good of the Milky Way."