Stop and frisk isn’t exactly a WMD, because it relies on human judgment and is not formalized into an algorithm. But it is built upon a simple and destructive calculation. If police stop one thousand people in certain neighborhoods, they’ll uncover, on average, one significant suspect and lots of smaller ones. This isn’t so different from the long-shot calculations used by predatory advertisers or spammers. Even when the hit ratio is miniscule, if you give yourself enough chances you’ll reach your target.
