Users do not search for anything in particular; rather, they spend time on StumbleUpon for one reason only: to discover new content that matches up with their interests. After StumbleUpon users document their interests on the site, the only thing they have to do afterward is click the “Stumble” button – sometimes over and over again. StumbleUpon itself works completely based on user preference, based upon whether somebody gives your page the thumbs-up. The more “likes,” the more StumbleUpon will send your page out to other users.
Read more at http://www.business2community.com/online-marketing/might-surprise-stumbleupon-0684002#sojZYu7X4OLoUuhq.99