Interestingly, this is very similar to the argument that record companies have made for years about bootleg audio and video of shows being made availible. I always note that allowing a zillion versions of their songs to be freely traded online has never hurt the touring revenues of acts like The Dead or Dave Matthews Band.

Great post Chris.

So, I think I have to disagree with your assertion. I'd argue that the for-profit conference is the equivalent of Old Media. It's the We Talk, You Listen model. I think unconferences provide so much more value and learning potential. I base this on the experiences of a friend that attended her first PodCamp in Boston last month. She was just blown away by the fact that she could actually sit down and talk to people like CC Chapman, who have so much knowledge to dispense and that it only cost her $50. She made the point to me several times that she had gotten so much more out of PodCamp than any for-profit conference or seminar that she'd been to and paid hundreds or thousands for.
It all comes down to value and the Long Tail model. I think the bottom-up, no-big-names, crowd-sourcing model is where much of the world is headed and conferences are no exception. Making money from the control of passive, read-only information is an increasingly difficult model to make work. It's the conversation with a knowledgeable person that's worth money, not some dead information.