There are several reasons why comScore's and DoubleClick's numbers might not agree. The methodology used by the two research firms differ fairly significantly.
DoubleClick directly measures traffic from sites using Google Analytics, gathers data from Google products that individual users have installed like Google Toolbar, and also uses third-party market research.ComScore, meanwhile, captures data from more than a million domains and combines that with a panel-based Internet measurement system that takes Web surfing data from about two million worldwide Internet recruited users and projects total page view numbers from that sample group.
The comScore methodology also weeds out a lot of data that may be allowed by DoubleClick. ComScore's recruited panel members are 15 years old at a minimum, which could account for disparities, while the research firm says it's also careful to discount numbers generated by spiders and bots.But comScore also says the potential for inflation of page view numbers isn't as high as it is for unique visitor figures, so it remains somewhat puzzling as to why the research firm and DoubleClick would have such wildly different page view numbers for Facebook.One thing's certain—Facebook and Google are head and shoulders above the competition in most any metric, though Microsoft's sites enter the discussion when it comes to unique visitors. Google was the first property to get 1 billion unique visitors in a month when it hit that number in June, according to comScore. Microsoft was second with 899 million and Facebook was third with 737 million unique visitors.In terms of page views, though, Facebook has been growing massively as its closest competitors have remained stagnant or shrunk.According to comScore, Facebook went from 249.9 billion page views in July 2010 to 467.2 billion in July 2011. Google's page view numbers went from 271.1 billion to 269.9 billion over that span, Yahoo's from 95.5 billion to 91.5 billion, and Microsoft's from 103.2 billion to 86.5 billion
