Picture this scenario:  you run a private residential facility for abused children.  Late one night, one of your computers is used to access pornographic web-sites and other inappropriate material in violation of several well-publicized workplace policies.  After further investigation, you learn that the inappropriate computer usage occurred on several occasions, but was limited to that one computer, which is located in an office shared by two day-shift employees in the administrative building.  Several employees have access to the building and could have used the computer on the nights in question.  Concerned that the culprit might be a staff member who works with the children, you hatch the perfect plan to catch him or her:  place a hidden camera in the office!  Of course, you don’t want to publicize its placement.  That would defeat the purpose and the guilty party would simply find another computer to use.  Besides, you plan to activate the camera only at night, several hours after the day shift has left the facility.  The daytime occupants of the office won’t care that it’s there.  Genius!