There is a brilliant article in business week online regarding podcasting. Highly recommended:
Don't Quit Your Day Job Podcasters
I do not agree with their all of conclusions as there are plenty of ways to "monetize" podcasts. For intance, product-tie ins can bring in revenue. On one of my podcasts, I am about to start selling digital downloads of the products that my interviewees sell. I do not expect it to make me rich (initially, anyway) but having a podcast with both information and consumer value might be a way to go for some podcasters.