All students who have taken a Social Psychology course have been exposed to the work of Darley and Latane on bystander apathy. The study followed the infamous public murder of Kitty Genovese. Research following the event attempted to understand why no one had come to her aid. By staging simulated events under different conditions, the research evaluated various hypotheses.
Obviously, bullying and cyberbullying provide similar circumstances and bystander apathy is often offered as an explanation for lack of intervention. Why are attackers not reprimanded by others? Note that encouraging peers to intervene online is frequently offered as a possible solution.
A recent study (I believe unpublished at present) has taken a similar experimental approach to studying cyberbullying (Dillon). The results are very similar to the old Darley and Latane research and just as disheartening. However, the manipulative methodology does offer a useful approach for evaluating the impact of whatever techniques are used to encourage peer support.