Podcast advertising will skyrocket over the next five years, climbing 400 percent to $400 million by 2011, according to a report released this week by eMarketer, an aggregator of e-business research. Podcasting's allure to advertisers can be attributed to the growing number of podcasts -- 90,000 and climbing -- and the medium's ability to target an audience.

>> Podcast Advertising: A $400M Business by 2011