Conferences along these lines often don't, and that seems to be the biggest disconnect, and the one thing TED has done superbly over anything else. It really needs to become a trend that, no matter how narrow the subject, posting a video of a talk online should be standard operating procedure.
It's the worst in academia, but due to lack of resource or even due to a preconception that people outside of the conference aren't interested, it's something that gets overlooked way too often.
If it's a big conference where you're already talking to a big auditorium, I could see that. If it's a small conference or workshop, though, it completely changes the dynamics of a talk if you're doing it to be recorded for permanent archival on the internet, vs. talking to 20 colleagues in a room. TED is explicitly a very public platform for charismatic public speakers, which is a good thing to exist, but not what every conference should be like imo.
I personally am not too great at public speaking and don't relish the idea of something I was talking about slightly awkwardly being on the internet forever, so if talks were regularly being recorded at some conferences, I would probably just not submit to give talks at those conferences. Not all of us are TED speakers! I do try to make my stuff freely available and accessible in the medium I'm more comfortable in, though (written text), by
writing accessible blog-style expositions, in addition to putting up PDFs of full papers.
Keynote talks are a bit different, since they're invited specifically to be big public talks. So for those, yeah, maybe it should become routine for them to be recorded/archived. Fortunately, those are also the ones that often have the broadest interest.
Seems like a great opportunity for people with the means and connections to build a better biodome. Like how PAX ended up being a good alternative place to go once E3 got more exclusive.