Ian Lurie explains the top reasons why StumpleUpon's popularity has waned. "Links from Stumbleupon.com don't help with SEO," he says. "They 'nofollowed' everything a long time ago to prevent spammers from overrunning the place." And as for the traffic, Lurie says it "looks lousy. Lots of visitors, but their average time-on-site is so low you wonder if the visitors have their eyes open."
So why should SEOs still pay attention to StumbleUpon? Lurie says that the tool is a great way to drive PageRank improvements, link juice-passing, and inbound links from other, more authoritative sites. And he uses research from his own Web site to back up the theory.