Intelligent technologies such as performance support systems and decision aids represent a key aspect of modern sociotechnical systems. When new tools are introduced into the workplace, they represent hypotheses about how cognitive work is expected to change. The tacit hypothesis is that any such change will be for the better, performance will be more efficient, and decisions will be improved - that is, they'll be made faster and on the basis of greater evidence. Experience suggests that technological interventions sometimes have the intended positive effect. However, they often result in negative effects, including unintended cascading failures and worker frustration due to "user-hostile" aspects of interfaces.