That made me think of programs that are aired at the same time across the country, like presidential addresses or the Super Bowl. Twitter posted an awesome graph on its blog tracking Super Bowl-related tweets for both the game and the commercials. The blue line represents game-related tweets with explanations for volume spikes like "Saints recover onside kick to start the second half" and "touchdown Colts!" The red line represents commercial-related tweets with spikes for "Google commercial" and "third Doritos commercial."
Looking at the data is an interesting way to see what people were getting excited about; apparently by the end of the game, half of all tweets posted were Super Bowl-related. Obviously the same thing happens for major news events or product releases (I'm talking about you, iPad); but this graph is unique in its tracking tweets over time.