Power-Hungry cyberbullies seek to manipulate others with fear. They want attention and to see their targets react with fear. Some students who were once victims of traditional bullying find themselves as aggressors online because social media has leveled the playing field for them (Aftab speaks to the Revenge-of the Nerds subtype). The approach involves social-exclusion of targets to demonstrate the social clout of the instigator.
Although Mean Girls cyberbullies rarely threaten victims, they engage others to pass along messages filled with rumors, vote at cyberbashing sites, or other tactics to help spread humiliation. (In case you're wondering, cyberbashing sites allow kids to create humiliating categories, like school's fattest, dumbest, ugliest etc. kid, and vote).