Take it from Upworthy’s top curator, Adam Mordecai: "Rarely, if ever, does content truly go viral ... I think 0.5% of everything we do goes beyond one million views."
Addendum (12/31/2013): Put another way (again from Mordecai): "Anyone who says they can make anything go viral is probably a snake oil salesman or really naive. Most of our stuff fails."
Addendum (1/8/2014): One more Mordecai slide:
