Despite the increase in quality, I find myself going to fewer and fewer talks in general theory conferences. I learn much more talking directly to my fellow computer scientists. As for the presentations, I can read the papers later.
A fellow computer scientist suggested that we hire a company to videotape the talks and make them available on the web. A back of the envelope calculation suggested we could make this happen for about $10 extra per participant for a reasonably sized conference. I am not a fan of making talks available on the web. Outside of a conference, who has time to sit at a computer screen and watch talks. I also worry about giving people yet another reason not to go to a conference. Remember the most important aspect of a scientific conference are not the talks and papers but bringing members of the community together.