Ian, you pose some interesting suppositions, but don't make the first (and most important) statement:

What is the purpose of podcasting?

I subscribe to several different and varied podcasts. All of them are really niche-"market" in one way or another, and none of them have what I would call "Johnny Nascar" appeal. Listener subscription numbers are nowhere near the volume of even small AM radio stations, let alone NPR, NBC, Fox, etc.

From my (probably flawed) interpretation of your article, it seems that you're looking for a way to "monetize subscribers" which is probably not going to happen with the current reality of podcasting. By that, I mean that a large proportion of podcasts are, to put it bluntly, amateur efforts in the name of something that the producers love. There are podcasts about sex, podcasts about (and by) sex-workers, podcasts by TV show producers, podcasts by TV show fans, podcasts that are a new face to old-time radio drama, podcasts that are about life and death and everything between. I've seen podcasts that are only audio, I've seen slideshows that have a sound-track, and I've seen video podcasts.

Yes, there are some podcasts that are crap production quality, and some that are professional-grade. I've listened to some (briefly) that frankly bored me to tears, because the host(s) just didn't have "it" while on the other side, there are some podcast personalities that have had me hanging on every word, and then there's the vast majority: Regular folk, talking about something that they are passionate about.

To say that "podcasting is failing" is disingenuous at best. Are historical reenactors "failing" just because they don't meet someone's marketing idea of what a success is? Not on your life. We do it because it's an act of love for the subject, and most of us are more than happy to talk about it to no end.