SunCEC2007: Metric of interestingness

How can you measure the interestingness of a keynote? It´s really simple. My colleague Gerd observed, that the more interesting a keynote was, the less notebooks were active. Thus the metric to measure the interestingness would be the count of notebook backlights. Or as I suggested to him for automating this metric: Simply count the active MAC addresses on the WLAN routers.