Caddyshack, a favorite movie from my teen and college years (oh, who am I kidding — it still cracks me up!) includes a scene with the late Rodney Dangerfield in which he’s on the phone with his stock broker. Dangerfield plays an obnoxious nouveau riche land developer by the name of Al Czervik.

Excitedly Czervik shouts into the phone: “Buy, buy, buy!” and after a pause to listen, “They’re all buying? Then sell, sell, sell!”

That last piece of advice now appears to apply to stocks in the broadcasting sector, according to a report in BusinessWeek, which includes this ominous quote:

Meanwhile, traditional broadcasters will probably remain challenged by secular factors such as audience fragmentation, as advertisers shift more spending to the Internet and other new media platforms, Amobi says. A terrestrial radio recovery could be impeded by a continued supply and demand imbalance, while the satellite radio companies have also seen anemic retail sales, even as they await a likely imminent regulatory decision on their pending merger proposal. However, TV advertising offers a bright spot, in our view, with a relatively strong 2007-08 upfront and scatter market for the networks, and a specter of record political dollars for local stations with the upcoming Presidential elections.

To be fair, this isn’t exactly breaking news. Audience fragmentation has been the hallmark of the 21st century as media outlets and platforms proliferate and the old media companies actually accelerate their decline by reflexively going for ratings with sensationalist and over-commercialized programming.

And on the matter of TV advertising, what happens after the 2008 election cycle? That’s not a pretty picture, even if it does come in HD.