They also have subscribers who are very serious about the products and services. If you choose to go with television or radio advertising, the same holds true. If you listen to your local radio stations on the weekend you will usually find that talk stations are packed with smaller radio programs that target a specific audience. In my hometown the main talk station has shows on, among other things, shooting, horses and computers. If you sell those products, you can really take advantage of the more specialized customer base.
Television works the same way.
It's the viewership, or demographics, of the show. If a program draws the types of customers that the big advertisers are looking for, the show stays on the air. If not, it perishes. On the Internet, you can do this on the major banner exchanges very well. They allow you to target your ad to specific types of site.