Diffusion of responsibility is a social
phenomenon which tends to occur in groups of people above a certain
critical size when responsibility is not explicitly assigned.
Diffusion of responsibility can manifest itself
* in a group of peers who act or, through inaction, allow events to
occur which they would never allow if alone (see bystander apathy
for an example) or
* in hierarchical organizations as when, for example, underlings
claim that they were following orders and supervisors claim that
they were just issuing directives and not doing anything per
se.