I left a long comment about Podcasting and MeshForum on Mark Cuban's blog this afternoon.
It is important also to realize that some Podcasts - like IT Conversations (which is a mix of conferences, radio shows, and new content - are at a level of attention well past what most streaming online radio shows ever reached - IT Conversations gets as many as 20,000+ people to download each show they release (and that was pre-iTunes, I suspect they may reach 50,000+ on popular shows pretty soon) with over 100,000+ monthly unique listeners.
Those numbers are compelling.
They also are changing the conference business in some radical new ways.
My conference - MeshForum (http://www.meshforum.org) reached 50+ people in person in our first year. A respectable turnout for a first year conference on a complex topics (Networks - social, technical and physical).
Via IT Conversations, where our first session has just gone live this afternoon (see http://www.itconversations.com/series/meshforum2005.html) we will reach probably 20,000+ different people with at least one session from MeshForum 2005.
That is a 400x increase in our reach.
A year from now when we hold MeshForum 2006 that increased reach can only help us - by helping get great speakers and participants but also by yet again increasing our reach to I would guess 50,000+ people for MeshForum 2006.
As a conference organizer this changes how I structure the conference - I have a new and very important audience to consider.
As a podcast listener the content I get from podcasts is content that for the most part does not exist anywhere else. It resembles the best of independent radio (or in some cases the best of public radio) but it is much more focused, liberated of the constraints of the FCC, and in nearly all cases (and all of the cases that I listen to) driven by personal passion.