The Justice Department has begun an antitrust investigation into Yahoo's test of Google's search advertising technology according to an anonymous source cited by Reuters:

The source, who spoke on condition of anonymity, said that some of the government's concern focused on a telephone call from Google Chief Executive Eric Schmidt to Yahoo Chief Executive Jerry Yang to offer help in thwarting Microsoft's $44.6 billion bid.

Microsoft has to be giggling like The Joker if Schmidt's attempt at swooping in like Batman leads to a date with Gotham City D.A. Harvey Dent.

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