http://soshable.com/stumbleupon-surpasses-facebook-for-social-media-traffic-generation/
How can a site with 12 million users send more traffic than a site with 600 million users? When your site is specifically designed to do nothing but send traffic. StumbleUpon may be small compared to sites like Facebook, Twitter, and MySpace, but it sends the most social media traffic around the web according to the latest numbers by StatCounter.
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