A San Francisco federal judge on Thursday night ruled that technology company Bazaarvoice Inc. violated U.S. antitrust law when it acquired a rival firm in 2012, a notable win for the Justice Department.

U.S. District Judge William H. Orrick III ruled Bazaarvoice's $168 million acquisition of PowerReviews Inc. unlawfully threatened competition in the market for Internet services that retailers use to collect and display online product reviews written by consumers.

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