(Your quoting is slightly broken.)

Hacker News uses this sort of system: there are thresholds for things like being able to vote, being able to downvote, etc., and they are all based on your karma score. The same is true on Stack Overflow, though that's a very different kind of site.

Both of them see frequent complaints that they're going downhill, but it's hard to be sure whether that's anything more than standard "the world was better in my young days" thinking (which I think results from a general tendency to remember good things better than bad things).