An Undertaking of Great Advantage, But Nobody to Know What It Is: Cosma Shalizi summarizes and links to a Wired report about an FBI data mining project. Leaving aside constitutional and political issues, what stuck me most in the report is was the following quote:
[...] the Justice Department claims that with this new data mining center’s access to billions of personnel records the “universe of subjects will expand exponentially.”(Via Three-Toed Sloth.)
If the “universe of subjects” will expand exponentially, so will the universe of false positives for a fixed acceptance rate. Since the FBI's investigative capabilities cannot grow exponentially for demographic reasons, their only solution would be to decrease the acceptance rate of their data mining procedure. Given their past problems with false negatives, I'm not sure that would be tenable. Unless their data mining methods are getting exponentially better, which in my experience never happens.
Lest I sound too negative about data mining, here's a high-accuracy data mining rule: When high-ranking bureaucrats use the adverb “exponentially,” they are deluded or being economical with the truth.