Karma scores are doubtless a powerful force, and I have no doubt that they will do exactly what Robin suggests that they will. I don't think you can have one without the other, unless you find a way to reward karma for external activity. However I strongly agree with khafra that it is very much a happy problem at this stage to have some people a little too concerned with their karma scores. The bias towards doing what can be scored seems likely to work for us in at least the medium term.