Impression fraud is a special case of click fraud. The prototypical impression fraudster is the competitor who resorts to unfair means to gain an advantage. His primary motivation is to reduce the ranking of his competitor, and then save himself money by inserting his own ad at a lower rate. Another possible motivation may be a hit-and-run operation(random act of violence). Given the potentially devastating consequences it could have on a person's web site return on marketing investment, it could even be a disgruntled employee.