Real-time, crowd sourced data

"Folks were tweeting 5,000 times a day in 2007. By 2008, that number was 300,000, and by 2009 it had grown to 2.5 million per day. Tweets grew 1,400% last year to 35 million per day. Today, we are seeing 50 million tweets per day—that's an average of 600 tweets per second. " via Twitter Blog: Measuring Tweets.