Business Week is hyping the advertising potential of podcasts, calling them The Next Big Ad Medium.

According to their analysis, podcasts are poised to grab a larger slice of the multibillion-dollar online advertising pie. They highlight research from eMarketer expects that advertisers will spend more than $400 million on podcasting by 2011, up from $80 million last year.

The increase of video podcasts, which lend themselves to the kind of video ads that marketers are accustomed to developing for television, has also increased advertiser interest. Also expected to entice advertisers is the highly targeted audience of many podcasts, says Belcher. For example, there are podcasts for people interested in consumer electronics, skateboarding, and comic books. “You can really serve a niche much better than traditional television,” says David Prager, chief operating officer and VP of programming at Revision3, an online television network that shows video podcasts. Its most popular, Diggnation, is viewed 250,000 times per week, Prager says.

The more targeted the audience, the more likely advertisers can reach a consumer willing to buy their product. And in theory, that increased targeting will at some point lead to higher-priced advertising.

Fueling the anticipated growth is the expected entrance of Google into the podcasting arena, as well as the emergence of podcast services focused on addressing the needs of advertisers.