In the middle of last year, Google started suspecting that Bing was ripping off their search results. So they did what any nerd does when they think someone is ripping off their answers on test day: They made shit up.

Google injected "synthetic" results into its search engine — fake queries and results that no real user or engine would ever generate. Then, on D-Day, December 17, about 20 Google engineers were asked to run the test queries with Internet Explorer 8, Bing Bar and Suggested Sites. By December 31, some of these fake results began appearing on Bing.

Oh, shit! You can read much more about the whole sordid affair at Search Engine Land.

UPDATE 11:36 am: Bing's corporate vice president confirms that they do this, suggests that every search engine should do this, and accuses Google of pulling a "“spy-novelesque stunt.”