Why are there no Comic-Con panel webcasts?

I'm a bit of an American politics junkie, so I've been looking forward to next week's Netroots Nation conference in Pittsburgh, though I wont be anywhere near Pittsburgh while it's on. Last year they recorded live video feeds of most of the panels which you could then watch on the web whenever you wanted, and they are planning on doing the same this year.

I can't understand why all the major conventions (especially the just completed San Diego Comic Con who are really the best placed to make a move like this) don't do the same. Sure they couldn't do it with all the panels, especially the movie presentations that are generally meant to be sneak peeks, but there is really no reason why the other panels and Q&As cannot be webcast.

There would be costs involved, but I imagine they could be offset by including some sort of advertising material in the videos. Attendance levels wouldn't necessarily be badly affected, if anything San Diego's current problem is that it can't meet demand - something that this may partially ameliorate. Its not as if websites like Newsarama and Comic Book Resources are not already doing just about everything except broadcasting video of these events, what with all their liveblogging and constant updates.

These events must generate huge traffic spikes for those websites. I don't see why the cons themselves shouldn't see a piece of that profit. It wouldn't even necessarily mean a loss of traffic for the news sites - in fact it would be in the cons' best interests to allow embedding of their videos so that they would be distributed as widely as possible. It might even mean better con coverage, with reporters forced to find their own stories rather than the current situation where we get endless pieces transcribing the same quotes.

I'm guessing that the reason this has not happened yet is that the cons are worried about the legal issues involved, and whether they would have to pay panel participants. I think that issue could be overcome though, as most panelists participate for promotional reasons, so wider and better distribution of their appearances would be to their benefit as well.