Welcome to the “YouTube effect.” It is the phenomenon whereby video clips, often produced by individuals acting on their own, are rapidly disseminated worldwide on websites such as YouTube and Google Video. YouTube has 34 million monthly visitors, and 65,000 new videos are posted every day. Most are frivolous, produced by and for the teenagers who make up the majority of the site’s visitors. But some are serious. YouTube includes videos posted by terrorists, human rights groups and U.S. soldiers in Iraq. Some are clips of incidents that have political consequences or document important trends, such as global warming, illegal immigration and corruption. Some videos reveal truths. Others spread propaganda and outright lies.Fifteen years ago, the world marveled at the “CNN effect” and believed that the unblinking eyes of TV cameras, beyond the reach of censors, would bring greater global accountability. These expectations were, to some degree, fulfilled. Since the early 1990s, electoral frauds have been exposed, democratic uprisings energized, famines contained and wars started or stopped thanks to the CNN effect. But the YouTube effect will be even more powerful.