According to a Betanews story, Microsoft's Steve Ballmer was furious when he learned that Kai-Fu Lee was leaving Microsoft for Google. According to one witness, Ballmer vowed to "bury" Google. Ballmer denies that the incident occurred as described.
Editorial:
Whether true or not, if a competitor were hiring my guys, I'd probably say more aggressive things than "bury". At the level Microsoft and Google are, we should leave the comparisons with companies behind and look at them more like sports teams. I suspect the Cowboys and Steelers have had tougher words than "bury" in the past. 
But no matter how you look at it, the battle is on between Microsoft and Google. And to think only a couple years ago there were rumors of Microsoft buying Google.
