This post is an excerpt from So, Bing's Copying Off Google: What Now, Google?.
The Short Version
The long and short of it is that Google started making up "words" that no one would actually search for - "hiybbprqag" for example - and then linking them to unrelated results. The gotcha moment came when Google engineers searched Bing for those "words" (after weeks of using Internet Explorer, searching for those "words") and came up with those same results.
