Some 9.2 million U.S. web users - or 6.6 percent of the U.S. adult online population - have recently downloaded an audio podcast, and 4.0 percent, or 5.6 million people, have recently downloaded a video podcast, according to Nielsen/NetRatings (pdf). "The portability of podcasts makes them especially appealing to young, on-the-go audiences," said Michael Lanz, analyst, Nielsen/NetRatings.

Young people who are online are more likely than older counterparts to download audio or video podcasts. Those between the ages 18 and 24 are nearly twice as likely as the average to download audio podcasts, followed by users in the 25-34 and 35-44 age groups - also more likely than the average to do audio podcasting.

Video podcast downloaders trend a little older, with 25-34 year olds the dominant group, followed by 18-24- and 35-44-year-olds.