Karma has been a common forum feature for years, but never on the GMC. Until now (well, since last year actually).
The GMC Karma extension (exclusive to Firefox users) gives all users an initial karma of 0. Other members can then raise or lower each users karma, giving a reason as to their actions. It allows users to see what others think of them as well as showing why people have made their score as such.
At the time of writing, I have a karma of 2 (currently
). It has been raised twice. Once for humour and once for, I quote, "being Grego". It's a nice idea. On seeing this, I had a little chuckle to myself, amused at the idea that I was actually funny.
But what happens when your karma drops? Muslim_power's karma is, at last check, below -10. How does that make someone feel. Reasons for MP's low karma are "racist remarks" and suchlike, a lot of which are misunderstandings. This is when karma becomes a bad idea. If people have low karmas, it might make them upset or encourage other users not to download their games. I personally would find a low karma quite fun, but I'm sure others wouldn't and my bear a grudge against me for it.
The problem here is that there's no way around the situation: moderator's couldn't technically moderate all karma changes, but that would mean a lot of work for them; you could disallow lowering karma, but many members deserve it; the same goes for not letting karma go below 0; users could choose to opt out, but would that really be fair or sporting?
There is no real way to stop people lowering karma for the wrong reasons. Take a look at a Ablach Blackat's for instance. He's been lowered for giving someone a warn and because he's "mean". Moderator's have a lot of trouble with this sort of thing, being attacked for doing their job and, generally, doing it well.
Karma has its advantages and disadvantages and I think it's fun as long as it's not made serious. It was initially intended for fun, rather than to make a defining judgement about a person and that's how it should stay. So, as long as you can take a joke and have a bit of fun, find out your karma: