Nearly 1.1 trillion display ad impressions were delivered to US Internet users in the first quarter of 2011; among them, Facebook accounted for 346 billion—31.2% of the total display market—nearly twice the level delivered one year earlier, according to data from comScore Ad Metrix.
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http://www.marketingprofs.com/charts/2011/4997/facebook-nabs-nearly-one-third-of-display-ad-market#ixzz1guz1aG5I
