Only the Facebook, Twitter and co of the world. Ever seen a segment with some open source software? Personally never.
If by media you mean mass media it's very simple, economic reasons. These corporations often give money to news corporations for articles being written about them. If you have the money, you can get more marketing and users easily. People who create open source software usually don't have a lot of money.
There is money in open source if you mean non-traditional media (websites, youtube).
It's evident for privately own propaganda outlets, but why doesn't public broadcasters don't speak about it too? There is quite a lot of very useful solution in the open source world... Linux, BitTorrent, copyright free educational material, lot of softwares... What can't you do with open source?
