Tagging, the emblematic activity of the “Web 2.0″ and social computing era, appears destined for mainstream status, a new study concludes. Among U.S. Internet users, 28 percent have tagged online content like blog entries, photos, Web sites, video clips, and news articles, The Pew Internet & American Life Project reports in a study released Wednesday. On any particular day, 7 percent of users engage in this activity to categorize and label material they upload or find on the Web. Justen Deal, a manager in Los Angeles who tags news articles on sites like Slashdot, believes that as the use of tagging increases, it will give blogging and the Web in general a significant boost by making content easier to organize and discover.