Do you know GIS users who check their GIS analyses results by hand?  I do.  This speaks volumes of those systems’ reliability (or rather the users’ perception of the systems’ reliability, which is what matters).

A test saying a woman is pregnant when she is actually not pregnant is an example of a false positive [Wikipedia].  Computer systems are riddled with false positives – antivirus software and email spam filters are two examples – and GIS are no exception.  False positives lower the users’ confidence in the systems and set the stage for false positive fatigue – the phenomenon when the system users become desensitized to the deluge of false positives, and as a result tend to classify an actual positive as a false positive. (Remember the last time you paid attention to a car alarm?)

An interesting example of false positive fatigue is presented by the recent case of Mr. Andrew Speaker, who flew on crowded airplanes while infected with a dangerous form of tuberculosis.  False positive fatigue can explain the behavior of the US border agent at the Plattsburgh, N.Y., border crossing with Canada, who decided that Mr. Speaker did not look sick and so let him go, despite a notice to Customs agents to detain him [New York Times]. Clearly, the agent put higher trust in his personal experience than in the computer system.

Computer systems have become too complicated without getting more reliable.  It feels that some systems’ complexity has surpassed their utility.  As a result, such systems become a hindrance rather than a useful tool.  System reliability ought to always take precedence over whiz-bang functionality.  Simple is beautiful.