The best karma system I have seen was one in which the weight of votes depended on the karma of the voter. The example I am thinking of allocated weight vote according to 'rank' but when plotted the vote/voter.karma relationship would look approximately logarithmic. That system would be farm more stable and probably more useful than the one we have, although it is somewhat less simple.

Where were the logarithmic karma system used?

The stability could be a problem in the moderately unlikely event that the core group is going sour and new members have a better grasp. I grant that it's more likely to have a lot of new members who don't understand the core values of the group.

I don't think it would be a problem to have a system which gives both the number and total karma-weight of votes.