"The global human population can be regarded as geographically distributed, multimodal sensors"
When it comes to sporting events it seems that all you have to do is look to the twitter frequency. The system that they created seems to work for most games. The exception to this is the Super Bowl for the reason that the sheer number of tweets about the game saturated the Twitter distribution system and so they couldn't pick out the maximum in tweet frequencies. They also have some interesting observations on how fast tweets follow an event.