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That's what the addition by subtraction equals when you compare comScore's 10.8 billion unique video streams counted in June to Nielsen's 7.5 billion — because of the two Web usage statistic compilers, Nielsen refuses to count "pornography" and "advertising" in the company's total.

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http://valleywag.com/5046534/porn-and-ads-account-for-two-in-five-videos-watched-online