Stumbleupon is still driving FIERCE traffic folks. In fact, StumbleUpon is now the biggest traffic driver among social media websites in the US, according to global web analytics service StatCounter. In fact, Its now a bigger traffic driver than Facebook. StumbleUpon is rolling out a new version on Sept. 1st. Watch for killer changes. Stumbleupon unseated Facebook at the top during June 2011, according to the latest StatCounter social media data. StatCounter tracks hits to over 3 million websites, and its social media data is gathered by analyzing every hit referred by a social media site.