The U.S. Geological Survey (USGS) uses tweets to corroborate earthquake occurences. They ignore tweets with more than seven words or that have a link or a number. They’re basically look for tweets like this:
earthquake?— ಠ_ಠ (@MikeIsaac) October 7, 2013
Clever. I wonder if this same method could be used to track other data (e.g. crime, car accidents)?