Just a thought from my side.
One sad thing I noticed on many boards.
If there is no reputation system, you won't get much positive feedback on your advices. Negative - of course, but I barely get a "thank you" or "helped me a lot" from the users, although they write on other or even the same board a few days later, that "this and that" worked fine for them.
But, as soon as there is such a system, people do it. That makes me asking myself - why do they?
I think it's because if you give positive reputation, you hope you recieve them either. It's like with the many "photo"-Sites we have here in Germany. People with ugly photos get many positive comments, just because the write 100 a day and know 300 people and everyone feels that he HAS to give something positive back and nothing different. If someone gave you 20 positive comments on your pictures and already got 20 positive for his pictures - who is brave enough to say "sorry, that is really not good, because... (honest and correct explanation to follow)". From what I've seen and read, nearly no one.
I don't think that everyone acts like that, but I also don't think that everyone uses negative reputation as a weapon. There will be a minority that will misuse these things and that shakens the whole stuff a lot (just as Rich said in the first posting).
Imho - I don't need the system, I don't look at the points or something. Perhaps we'd all do better if we say "thank you" or give positive feedback a little more often - perhaps per PM - but don't get into the trap of YOU MUST give the feedback or "the user has 400000 points - I CAN'T give HIM a negative comment." I think it's a main aspect of a discussion to get positive and negative comments, that's the only way to improve yourself.
...my 2cc and greetings
Michael