Have you ever been the target of cyber-bullying? What was your reaction?
I'm not sure what "cyber-bullying" is. Bullying in school worked because there was an inequality of power that allowed them to get away with it, and retorting to them in-kind would result in worse which you couldn't counter.
Here, if someone says nasty things to you, you can respond with just as nasty retorts, ignore them, or whatever you feel like, and the worst that can happen is they say nasty things again. If it's Email, you can delete it without reading, if it's in an online forum, everyone else can see it too and it'll become obvious what's happening.
So I really don't know. I've had people say nasty things to me, I've had people announce with great drama that they were going to "drive you out of this group" or "shut you down" or whatever, but they had no power to do so and I just mocked them a lot. The closest I suppose was one guy who threatened to sue me for saying the truth about him (that he was a whining stalkerboy with no life), and as he has a history of actually suing people I decided that the amusement of calling him a stalkerboy wasn't worth the small but actual chance that he'd sue and thus cost me a lot of pain-in-the-ass for my whole family. But that's, to my mind, not the same as bullying.