Podcasting has a lot of buzz about it right now, but how big is it really? In the US, the radio consultants Bridge Ratings have come up with some interesting figures. Based on interviews with radio listeners, they reckon that 4.8 million people downloaded a podcast from either a radio station or other source in 2005. iTunes was referrenced as the most often accessed portal for podcast downloads. This 4.8 million estimate is up from 820,000 podcast users in 2004. They reckon the industry will hit critical mass in 2010. By then, they say between 45 and 75 million people will be tuning into podcasts in the US alone. I think that is too far out. One of the interesting points about new media is that tipping points accelerate, and products take-off much faster. than they ever did in the past. Still, regardless of the dates, the podcast universe is set to grow tenfold in the next few years.