Feeling guilty about whiling away all your time watching YouTube? You’re not alone. Sixty percent of U.S. Internet users watch online video regularly, according to a report released today by eMarketer. That’s 107.7 million people, or 87 percent of U.S. broadband users (the 60 percent we mentioned first includes dial-up). The firm expects that number to increase to 157 million by 2010, or 53 percent of the U.S. population.