StumbleUpon Bigger Than Facebook?

in one measure, at least. We spotted this today:

"Web discovery engine StumbleUpon is now the biggest traffic driver among social media websites in the US, according to global web analytics service StatCounter. The company 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."

Statistics Source: GigaOm. We have written about Facebook valuation and other Facebook statistics before.