I have watched a lot of shows & movies with cyberbullying & it is really scary (esp for younger people).
I can prevent this by filtering the circle of friends I have. The first sign that I am being bullied, I will have to talk to my parents (or any trusted & concern adult around me). I will not reply or retaliate in anyway. It happened to me once ( as an adult already) but I ignored the threat & mean messages/comments. Then I should send personal messages to my 'real' friends that my site/profile has been compromised or hacked that I will need to delete it. I will lay low for a while, pretend nothing happened; regain my confidence, be with real people (in person).
Bullying is a front for cowardice & lack of attention from loves ones. So be happy you are loved & cared for that you don't need to be mean to catch love & attention.
I hope this isn't too much...