The document summarizes several theories related to the impact of Web 2.0. It discusses Tim O'Reilly's six principles of Web 2.0, including user-generated content and the long tail theory. It also outlines theories by Chris Anderson, Charles Leadbeater, Don Tapscott and Anthony Williams, Dan Gillmor, Clay Shirky, and Michael Wesch, focusing on how digital technologies enable new forms of collaboration and participation and how this has impacted industries like media, gaming, music, and news.