[gwern]

Yes, wisdom-of-the-crowds or Condorcet's jury theorem are very similar.

(Now that I think about it more, there's also a lot of potential advantages to Twitter: global coverage, uniform data access, less risk of 'juking the numbers', less criteria drift over time... Yes, maybe local police records are much better, but you could spend a lifetime trying to get copies of them and putting them into the same data format and reconciling differing definitions etc.)