Pandora is popular, more so than Clear Channel, Cox and the rest of the pack. Again listeners are searching for something more than the same 200 songs over and over and over.
When people use Pandora, they listen to the same 200 songs over and over. The difference is they are THEIR favorite songs. They don't have to hear songs they don't like or know. Once again, it's not the number of choices available, but the customization. Also, Pandora isn't "more popular" than OTA, but used in conjunction. Once again, programmers and consultants are testing listeners to see if they really want bigger playlists, or less repetition, and the consistent feedback from all demos is that the majority isn't searching for more choices. Just more customization. If there was money to be made in OTA radio with bigger playlists, you'd have them.