Does Net radio pose a threat to local broadcasters?

Mike Langberg of the San Jose Mercury news believes so. He just finished up a week-long Arbitron ratings survey and noted that he spends far more time listening to online news and music that traditional over-the-air broadcast stations, something the survey does not take into consideration. (They do have a separate set of ratings for online stations.) I'd have to agree with Langberg. When I work from home I tend to listen to my local NPR station online for my dose of morning news then switch over to my own collection of digital music or an online-only station like Yahoo's Launch.