Sean Carton over at Publish has a pretty decent article on why podcasting is taking so long to hit critical mass. Carlton opines that while technology changes quickly, people change slowly but businesses and people do things for different reasons.
Just because the technology exists doesn't mean that everyone's going to jump on the bandwagon right away. Technology changes quickly. People change slowly.
But businesses...well, that's a different story. Businesses are driven by different motives than people and exist in an environment where a competitive edge--any competitive edge--can make the difference between success and failure.
I think Carton has a good point. He draws the correlation between WWW penetration and business adoption and it's a pretty good argument. Currently, podcasts are largely produced and listened to for entertainment purposes. While there's certainly a lot of money in entertainment in general, it's all driven by the big movie houses, television stations, and gaming companies. Until (if?) those big guys start using podcasts to advertise, podcasting isn't going to have the money it needs to success.
Business is different from real life. In business something must make money for it to survive and podcasting is looking pretty sickly right now.