I think stack overflow website has done more good than any other website out there, including facebook and anything google has done (the jury is still out on Wikipedia).
It has collected incredible amount of knowledge which is distributed for free, completely free, you don't even have to login and they play search engines in such a way that any problem I have with any programming project, the search gives me the answer on stack overflow.
It is pretty addictive to answer questions and watch as the points roll in, but it is also extremely demoralising to be awarded a negative point, which means you answer a question which someone, anonymous, don't like or agree with, he gives you negative points, so it actually hurts your high, and has damaging effects, no matter if your answer is actually correct.
I answered one question about which books and information someone should read to get better at Core Data. I listed the books that helped me, with Amazon links to follow, and I used amazon link shortener because amazon links are very long and very ugly. The results were that I raked in negative points and lost the important points that at the time pushed me above the very much sought after 1.000 points and left me at 997 points, like it was mocking me.
This has happened a few times and every time I vouch to quit answering questions on Stack overflow only to see a question lingering to which I know the answer and I say to myself, oh man, Stack overflow is actually so good, it is worth while even if you get punched in the stomach a few times, here and there.
I do understand why you could get negative points, lets say there is a C# question, and I would chime in and tell the person this problem did not exist in C++, which is totally trolling and unhelpful.
I suggest here inside my /dev/null nothingness, my empty wasteland of blog that if you vote down a question so that it gets a negative rating that you have to write a comment on why you did such heinous act, it could even be anonymous to the victim, but then the victim could fix the issue you have or even delete the post. You should at least know why your answer was so bad that it required you to be beaten up, why your score high was cut short and you would get a way to appeal this and the voter who voted you down would be forced to justify his deeds. You are not required to do so if you vote down, only when you vote down below zero.