*LOL* This remark about hacking being too easy for qwerty made me laugh. You really have a point here. I propose to cut qwerty's karma by half right now for this very reason, no matter if and how the karma sytsem will be changed.

But seriously, I'm not sure about the "invested effort" vs. "usefulness" stuff. Coming from the "karma is a measure for community involvement" camp, I am in principle against the idea that only useful things earn you karma.

OTOH, I agree it would be cool to have some measure of "how useful are my efforts to the community". That's why I think that it makes sense to count posts as one thing, but thanked posts as another (with a higher ranking). And it makes sense to qualify blog posts and applications via their rating (or maybe download numbers).

Still, I would be very unhappy if in the end the karma value would only reflect quality instead of quantity. As long as the (estimated) quality criteria we can somehow get hold of are part of the calculation and can be viewed as such in the user's profile, it should make both camps happy.

Maybe - this is just a quick idea while typing - it would work if the "posts vs. thanked posts"-system is applied to other parts of the calculation.
My profile shows
This could work for blog posts (count all of them, but show "thumbs up" for the posts according to "thanks" on a new line), applications (numer of apps vs. rating for apps) and so on. As it shows two distinct parts of your activity: One thing is what you do (write a blog entry), the other thing how it's received in the community (number of thumbs up).

Once these things are separate, you can check how useful your contributions are - which is part of your karma, but not all of it.