It truth, about the dozen or so media companies that have an effective oligopoly of *major* media, need to be broken up in antitrust actions.
But the devil is in the details of how to do this.
Some of these companies have vertical monopolies, such as Clear Channel Communications. With 900 stations, Clear Channel is the largest radio station group owner in the United States, both by number of stations and by revenue.
However, other companies lean more towards horizontal organization, such as Time Warner, which covers the spectrum of movies, TV, magazine-book-newspaper publishing, broadcasting, cable, etc.
http://en.wikipedia.org/wiki/List_of_assets_owned_by_Time_Warner
This is the media oligopoly:
Disney, “New” Viacom (and its former parent CBS Corporation, the former “Old” Viacom), TimeWarner, News Corporation, and General Electric together own more than 90% of the media holdings in the United States.
No worries, Dear Reader will control the horizontal and the vertical. ;-)