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What: Shares of Millennial Media (NYSE: MM) have plunged by over a third today, down by 39% at the low, after the company announced earnings and an acquisition.

So what: Revenue in the fourth quarter came in at $58 million, which was short of the $62.9 million in sales that the Street was modeling for. Earnings per share totaled $0.03, which was on target with expectations. The company also said it was acquiring Metaresolver in an all-cash deal, but declined to disclose the purchase price.

Now what: Outlook was also soft, with first-quarter revenue expected in the range of $48 million to $50 million, and full-year sales should be $270 million to $280 million. Compare those forecasts with consensus estimates of $56.7 million in revenue in the first quarter and $290.1 million in sales for 2013. CEO Paul Palmieri said revenue was light because the company didn't pursue some smaller deals and several larger deals did not close.

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