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Does Mark Zuckerberg read Valleywag? Facebook's young CEO isn't known for taking unsolicited advice, but we suggested he hire Google executive Sheryl Sandberg just two weeks ago. Well, that was fast: BoomTown reports Sandberg's been hired as Facebook's COO. Sandberg is Facebook's first woman executive, and she's older than Zuckerberg's 20something brain trust. But demographics are not the reason this hire is striking.

Sandberg ran Google's AdWords, the mostly automated online-sales operation which provides most of Google's revenue. Facebook has launched a similar self-service offering, though it's not anywhere near the scale of Google's. Sandberg's hire means that Facebook has serious ambitions to challenge Google in online advertising — not by courting Madison Avenue with well-paid salespeople, but by taking it on directly in advertising technology.