Activision Blizzard Inc. said that its Call of Duty: Black Ops has earned $1 billion in sales after just 42 days on the market, and is in the running to become one of the biggest entertainment releases in history, whether in movies, books or video games.

In comparison, the last video game in the series, Call of Duty: Modern Warfare 2, took 64 days to pass the billion-dollar mark.

Black Ops users so far have logged more than 600 million hours of online play -- or 68,500 years, The game, which allows group play, "is a social networking tool" making this area of Activision's business model closer to Facebook's than a typical video-game manufacturer.

In other news, Activision Blizzard Inc. on Tuesday added archrival Electronic Arts Inc. as a defendant in a $400 million lawsuit against two former executives related to the "Call of Duty" franchise. Activision in April counter-sued former executives Jason West and Vincent Zampella, saying that they tried to hijack the company's assets, threatening the franchise's future.

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