There's recent Netcraft story, Podcasts help drive demand for high-volume hosting, that notes
As podcasts and video blogs consume disk space and bandwidth, will these large media files reside with major web hosting providers, niche startups spawned by the Blogosphere, or perhaps Yahoo or Google? As Internet traffic shifts from text and images to video and audio, old hosting business models are being reworked and new ones imagined in anticipation of huge growth for user-generated data.
Indeed, there are huge pricing pressures going on, with a low end of 1.5 terabytes/mo for $14.95/mo of server space. If you take as your unit of measurement the 21 megabyte, hour long podcast of KCRW's Good Food that I listen to every week, that's roughly 150,000 weekly listeners that you can support for that level of bandwidth, or a low $1 CPM to reach them. That's pretty good.
What then will be the limiting factor for the growth of user-generated data? It's probably the quality of the broadband connections that home users have for listening in, and in some case for uploading files. The latest news from Andy King's essential Bandwidth Report for November 2005 shows 63.8% of US home web users with broadband, and 12.8 broadband subscriber lines per 100 inhabitants. (This is just ahead of Singapore, and about half that of South Korea's 24.9 lines/100.) Read the report for the whole analysis - the projection is 70%+ broadband by early next year.
If you don't have a broadband connection at home, you're probably not listening to podcasts. How much you do listen if you do have broadband depends on time available in the day for computer or iPod listening - for me, there's enough programming to fill a couple of one-hour slots, but I don't have a commute to go through that's long enough. Has anyone figured out how many podcast-hours per day are being consumed? Of course you download more than you listen to in most cases.
If you do have broadband at home and the means or the desire to do your own podcast, you might not have enough bandwidth to regularly upload very much - lots of "broadband" accounts are capped at 384k upstream, or only 6x as fast as a modem. Workable (an hour's show will take 10 minute to upload) if you have a hosting provider, but you're never going to serve those files from your home servers.
Interesting statistics that I haven't seen are estimates from podcast hosting providers of how fast their subscriber's connection speeds are, and how that is changing over time.
UPDATE: Thanks to Jorn at Robot Wisdom for fixing my first math mistake - 1 hr is 21 mb, not 2.1 mb. That takes the numbers from the originally reported $0.1 CPM to $1 CPM - still not too bad.
UPDATE 2: Thanks to the commenter who pointed out an upload/download confusion - hopefully more clear now.