Stumbled across a few nice things related to quorum decision making recently. Remember how sticklebacks make their decisions? Well bacteria do it too, below is a great TED talk by Bonnie Bassler on how they communicate and how they decide to act as an enormous group.
Also came across this article on humans making group decisions in a Kasparov vs The World chess game. It gets the saliva flowing on how you can engineer good decisions.
Addition: Incidentally, I also think this talk is a great example of how to give a science talk. It's a little rushed (probably nerves) but the enthusiasm is fantastic and the use of visual aids is perfect. I'm giving a workshop on presentations so I've been thinking about this stuff a lot recently.