Personally, my favorite conferences schedule 20 minutes after every other session, in order to allow for more attendee-to-attendee discussion (specifically Balisage and TOC). These conversations tend to be more subject-oriented than the social conversations in the evening, or at least more oriented towards the specific subjects just seen and where they might be headed.

I also wonder if perhaps the people who give the lightning talks should also submit a video of their talk a day or two beforehand; and these could be posted immediately after the lightning talk is given. These have intense interest and this way you're always sure you didn't miss something spectacular.

RogerS