This article in Wired this morning reports that although the number of channels the average american receives in their homes has jumped substantially in the last decade, the variety of owners has not increased nearly as much and that most of the ownership is still centered in a relatively small number of media conglomerates.
Looking at the lineup on DirecTV, you have to admit that there's certainly some truth on the surface.
CNN, CNNi, CNNfn, TBS, TNT, HBO (all 5 of them), Cinemax (all three of them) and more are owned by Time/Warner/AOL.
Discovery, Discovery Health, Discovery Wings, Discovery Civilization, Discovery Kids, Home & Leisure, The Travel Channel, Animal Planet, The Science Channel are all owned by Discovery Networks. By the way, their ownership page reminds us that Liberty Media (owners of Encore, STARZ!, USA Networks, QVC and Court TV), Cox Cable, Advance/Newhouse (Conde Nast, Parade magazine, and newspapers in 22 markets) make up the owners of the company.
A&E, The History Channel, The History Channel International, and Biograhpy are all owned by A&E Networks. But they, in turn, appear to be owned by Disney, who also owns ABC, ESPN (and it's variety of channels), Lifetime, and daily newspapers in 7 markets.
The list goes on, but is oddly short. Now, I'm not saying that there isn't some editorial capability at each of these stations and networks, and of course the competition between the individual mega media companies certainly provides that things that are against one interest, but in another interest won't show up. However, it does raise questions about the credibility of the ownership diversity if not the content diversity.
For a more paranoid (and possibly detailed) look, check out TurnOffYourTV.com.