A new research paper says celebrities played an important role in spreading the news of Osama bin Laden's death one year ago tonight. Researchers tracked which accounts were mentioned in tweets about bin Laden and found that there were three distinct patterns. Mentions of "media people" spiked first, but they were soon outpaced by official media accounts. Celebrity mentions grew more slowly, but those figures became dominant as time went on and media mentions declined. "While media people and the mass media compete to be the first to report the news, celebrities use their social influence to help spread the news and stimulate discussions," researchers conclude.