soundboy wrote: As I mentioned before, http://www.slashdot.org" target="_blank is one of the biggest and oldest computer science communities and it works on such a system.
On slashdot, threads are often huge, with hundreds or thousands of posts each. People vote positively or negatively on each post, and with enough votes, each post is assigned a value, from -5 to +5 (or something similar, I don't recall). When browsing a thread, you can set a threshold, so for example, you can choose to read only messages with a +3 or higher. That way you don't waste your time reading through 100 trash posts only to get to the 6 or 7 good ones. Plus, all the good and bad votes end up reflecting on the user.
If you reread the first page of this topic you will notice that advocated the Slashdot system when this was first dicsussed over two years ago. But that was not what my question was about. I asked whether you know a system where karma is a good enough representation of a user's popularity and community participation.
Again, the only advantage a user on Slashdot has for a good karma is that his post might be read by more people. The user itself does not receive any karma count or benefits from it (but a slight advantage of posting with a +2 IIRC). That works very well for Slashdot indeed. Combined with the good ideas of only moderating posts in topics you do not participate in, only a number of moderation points every few weeks, and meta moderation.
What people in here want is that the user earns the karma, and it is not only the post itself that benefits. And that is something that I haven't yet seen done well.