Despite the success of a few podcasts, the vast majority have been hard-pressed to see significant ad income, reports BusinessWeek.

Podcasting has yet to reach a significant listener base despite the quick adoption of advertising by podcast creators. Only 13 percent of Americans listened to downloaded audio in 2006, and ad spending on podcasts reached only $80 million last year.

The lack of standards in the buying of podcast ads is one factor contributing to the slow influx of money, as are inconsistent measurement standards. Even shows ranking in the iTunes Top 100 podcasts have a difficult time cutting regular ad deals.

Another issue is that the shows are often run by amateurs who have other jobs to pay the bills. In lieu of ad dollars, some podcasters offer merchandise for sale by their fanbase.