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"What is Yahoo's incentive to continue to compete?" That's the question Clinton-era Federal Trade Commission competition policy director David Balto asked of the search advertising deal between Yahoo and Google. And that's just one of many questions that will be asked by the Department of Justice now that officials have opened a formal investigation into the deal, according to unnamed sources cited by the Washington Post.

Google's general counsel Kent Walker (pictured) feels it's a competitive deal, with the company arguing that Google's better contextual ad placement algorithms make both users and advertisers happy and that other competitors share and license technology amongst themselves. Not cited, but mentioned in passing? Microsoft, party to one of the largest anti-trust investigations in recent memory and currently desperate to get a sizable share of the search advertising business.