Ironic that it's called "karma", which is a complete perversion of the original religious meaning of the concept, perverted into a means of recording a "permanent record" of how antisocial or unsubmissive you've been to community opprobrium. Purely regressive adaptation of technology, and a crime against the spirit of those who created it.
Which, I guess, is kind of how Google works in the long run, and also would tend to self-select people into like-minded groups. Overall, I think that our options are somewhat limited -- we either end up in a self-selected community or in a self-selected sub-community. E.g. I was "repelled" by digg because any politically "liberal" comment I made would be downvoted to oblivion within minutes. While similar things would happen on reddit if, say, one said things critical of libertarianism, I didn't find this quite so frustrating, and simply learned to curb my views accordingly.
Here on Hackernews (which I find to be the most reasonable community since the glory days of slashdot) I have learned to accept that, say, being critical of Android or having anything nice to say about PHP is likely to lead to a lot of welts.
I have a feeling the first site to dramatically improve content ranking is going to explode.
Edit: Thanks mparlane. I was on my way out, but you are right of course. :)
According to those who subscribe, anyway. But whether you believe or not, karma is not decided by a committee of down-voting equipped readers, each with his/her own desire for points. That's not karma, that's polling or rating.