Well, it's a good reason to attend the talk. I think the primary audience is usually people that attended the talk so that they could look over the slides late

Well, it's a good reason to attend the talk. I think the primary audience is usually people that attended the talk so that they could look over the slides later (at least, that's what I've done with my conference slides). I agree with you, though -- I wish more conferences would allow speakers to simply upload video to YouTube. A lot of of the time the conferences have DVD sales a few months down the line and want you to buy the video of the talks instead of watching them online for free.