http://www.bullyonline.org/workbully/mobbing.htm
What is mobbing? The word bullying is used to describe a repeated pattern of negative intrusive violational behaviour against one or more targets and comprises constant trivial nit-picking criticism, refusal to value and acknowledge, undermining, discrediting and a host of other behaviours which are defined on my page What is bullying? The word mobbing is preferred to bullying in continental Europe and in those situations where a target is selected and bullied (mobbed) by a group of people rather than by one individual. However, every group has a ringleader. If this ringleader is an extrovert it will be obvious who is coercing group members into mobbing the selected target. If the ringleader is an introvert type, he or she is likely to be in the background coercing and manipulating group members into mobbing the selected target; introvert ringleaders are much more dangerous than extrovert ringleaders.