Mark and I both felt that the audiences were not engaged. That many peoples' open laptops, Blackberries, etc, distract them from the people in front of and around them. I think its a shame. A great many people (myself included) travelled to be at BlogNashville, and they spent the time looking at their screens, rather than the people around them. I believe that this is another aspect of future shock: That we have these distractions for which we have not yet evolved social norms.I totally agree, but not totally. ;-)
At vloggercon, I was monitoring the IRC channel to engage those people that were not able to attend in person.
That was worthwhile.
Sometimes I'll go to a website that the speaker is talking about, or look something, or someone, up on Google. That adds to what the speaker is saying.
Going through your email, reconfiguring your server remotely, or catching up on RSS feeds probably doesn't.
So some use of laptops at conferences are valuable.