http://www.ananova.com/news/story/sm_49785.html
Quick search on Google came up with that, I had heard of it.
Whats the point of being a vigilante? If you argue that it is for some overall good then that is fairly bad maths, NEGATIVE PLUS NEGATIVE EQUALS BIGGER NEGATIVE (Two wrongs don't make a right). If you argue that you want a sense of justice, then presumably you are either arguing that it would make you feel better, or that some higher power demands justice. I doubt personally that commiting any act of violence actually makes someone feel better in the long run, and I don't know much theology, but I would suspect a god would probably be a more effective judge than any human...
If you have been hurt and want to get back at people that hurt you, then that is fairly normal, but it is vengence, not vigilantism. If you feel an actual want to harm others, no matter how 'bad' they are in your opinion, then perhaps you should be looking at your own morality before you start dealing with others.
I don't know, I do understand to an extent the motivation behind it, but I don't think it holds up to reason particularly well.
