Yahoo paid $680 million to purchase the remainder of Right Media that it didn't already own. The search giant had bought a 20 percent stake in the privately held online-advertising firm in October. Right Media runs an online auction service for Web publishers to sell advertising spots more efficiently, and it says about 20,000 buyers and sellers use it. Right Media was started in 2003.

The online-ad-space business is getting intensely competitive, underscored by Google's $3.1 billion winning bid earlier this month for DoubleClick, which is currently developing an auction service for ad sales. Right Media's valuation has soared in recent months. Yahoo paid $40 million for 20 percent of the company in October, which would have put Right Media's total value at the time at $200 million.

The New York Times points out that Yahoo had been using Right Media's auction service to sell some of its own ad space since last year, and it was comfortable enough with its capabilities to buy it outright. It eventually plans to sell all of its non-premium ads through the auction service.

The Wall Street Journal adds that the data collected by Right Media's exchange could help Yahoo garner insight into the dynamics of the online advertising market that could bolster its own ad sales strategies. However, Yahoo executives interviewed by the paper said that their first priority will be to maintain the exchange's independence.

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