I don’t often agree with the Cato Institute, but it’s hard to argue with this: Data mining, a.k.a. warrantless surveillance, generates false positives 90% of the time. The “statisical likelihood of false positives is so high that predictive data mining will inevitably waste resources and threaten civil liberties…. Better interagency information sharing, investigatory legwork, in pursuit of genuine leads, and better training are what the 9/11 story most clearly calls for,” but data mining distracts from those goals.

Not to mention it’s illegal.