eMarketer estimates that the total US podcast audience reached 18.5 million in 2007. Furthermore, that audience will increase by 251% to 65 million in 2012. And of those listeners, 25 million will be “active” users who tune in at least once a week. Driven by this audience growth, US spending on podcast-related advertising (including sponsorships) will rise to $435 million in 2012, up from $165 million in 2007. The situation might change in time, but for now podcasts are mainly a desktop phenomenon as opposed to a mobile or portable one.