After a recent study showing that facial recognition technology is at a point where it can identify strangers with reasonable accuracy if they have Facebook accounts, the novel amateur crime-fighting technique seemed momentous.

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Credit-card companies monitor every purchase and can identify fraudulent ones with a high degree of accuracy, using rules derived by crunching through billions of transactions.

ECONOMIST: Technology

Quova claims to be able to identify web users' country of origin with 98% accuracy, and their city of origin (at least for users in the United States) 85% of the time.

ECONOMIST: Geography and the net