"This is actually why I left reddit. As the site grew, I became increasingly frustrated that anything I said contrary to popular opinion was mercilessly downvoted & derided, regardless of the actual quality of the comment."

I hadn't noticed this. In fact, I noticed the opposite -- that well-articulated comments taking controversial views still got upvoted. It was just a stricter quality filter. And anyway, it's easy to take advantage of reddit's predilections. A while ago, I read a great George Will column, and thought it deserved to be reddited. My headline was something like "Notorious Neocon George Will actually believes that..."

I left because it was getting boring and homogeneous.

From the web site's perspective, karma is a mechanism for internal calculations, and is in no way a measurement of your intellect or morality (?) or whatever else. And karma can't be turned into money for you, so why bother at all? :)

That's why a possibility of being downvoted never stopped me from commenting, be it reddit, slashdot, or YCnews.

One lesson that I learned from reddit in particular, is that if you are interested in the topic, you should read all comments, all the way down the page, because there might be something there, in the negative karma area.

I don't see any reason why karma couldn't be turned into money. Karma indirectly determines the value a user add to a web site. If the site generates money, karma could be used as reference value to estimate an amount of revenue share they could get back.

This is already how it works in open source even if there isn't an explicit karma value. If good developpers and contributors are detected they may get an offer for a payed mission on the project or even better a permanent job.

PG said for instance that a good karma could catch their attention. Some sort of benefit to getting a good karma.

It is preferable that karma benefit are not made public and taken for granted otherwise the system could be perverted.

Karma reflects what the other users of a system think of you. So it can be meaningful to the extent other users are good judges.

Karma and all sorts of voting in general have a flaw: they reflect Average Joe's opinion unless, of course, you have a narrow social/professional group as your user base. The broader your group the lesser are standards of your social website unfortunately. Wasn't it one of Reddit's lessons?

That's why I think there are two types of winners in this game: those with good implicit ranking mechanisms (Google, Flickr) and those with good human moderation (Slashdot). Those based on explicit voting are taking the risk of being taken down by broad and unfocused masses.

Well there are a couple solutions. One, you could tabulate votes based on the karma of the users. So someone with higher Karma gets bigger weight. That will probably focus the discussionsa and submissions a lot.

Two, you could have interesting comments, based on people voting them up or down, and their replies.

Also you could do some kind of geomtric progression instead of linear, or combine that with the voter's own karma.

... and besides, I believe the karma system can be greatly improved by taking into account sub-comments.