Edit: Okay, here's the thing: I think it would be more useful if karma was the average of our valuations; i.e. if you could, say, input '+10' or '-3' as shorthand for 'upvote if below this number, downvote if above' rather than simply 'upvote' and 'downvote'. What do you imagine the problem with this system would be?

Not exactly a problem but a lotof my votes would either be +1000 or -1000.