Upworthy has mastered the dark viral arts with a unique blend of A/B technology and lily-white earnestness. The staff scours the Web for "stuff that matters," writes multiple headlines for a test audience, selects the top-performer, and blasts it out on social media. It's a deceptively simple plan that's devouring the Internet, one Facebook Newsfeed at a time. The site nearly surpassed 50 million unique visitors in October, which suggests traffic comparable to giants like Time.com, and Fox News.