Startup DataXu has raised $6 million in a first round of funding from Atlas Venture and Flybridge Capital Partners, peHub reports. The company,  which was founded by MIT alums in 2007, didn’t return calls seeking more information. The site appears to be in beta. Just based on the descriptive material on its web site, it’s difficult to tell what DataXu’s unique value proposition is. There are dozens of ad exchanges seeking to pair marketers and publishers. The business is dominated by Yahoo’s Right Media.