While reading Paul Bloom’s The Baby In The Well article in The New Yorker, I noted the Willie Horton effect’s parallel to software testing:

In 1987, Willie Horton, a convicted murderer who had been released on furlough from the Northeastern Correctional Center, in Massachusetts, raped a woman after beating and tying up her fiancé. The furlough program came to be seen as a humiliating mistake on the part of Governor Michael Dukakis, and was used against him by his opponents during his run for President, the following year. Yet the program may have reduced the likelihood of such incidents. In fact, a 1987 report found that the recidivism rate in Massachusetts dropped in the eleven years after the program was introduced, and that convicts who were furloughed before being released were less likely to go on to commit a crime than those who were not. The trouble is that you can’t point to individuals who weren’t raped, assaulted, or killed as a result of the program, just as you can’t point to a specific person whose life was spared because of vaccination.

How well was a given application tested?  Users don’t know what problems the testers saved them from.  The quality may be celebrated to some extent, but one production bug will get all the press.