It may be a fine line with some fringe comments being downvoted when perhaps they shouldn't be, but without this it spirals out of control pretty quickly and th

It may be a fine line with some fringe comments being downvoted when perhaps they shouldn't be, but without this it spirals out of control pretty quickly and the entire site becomes useless. Look at the transition that happened to Digg and subsequently Reddit. These were sites that originally had thoughtful or interesting users that would often be more informative then the content link itself (it's currently like this on HN). It seems for a while the bad comments get downvoted and removed, but once enough of the community is diluted with a critical mass of 'useless' users, bad comments start being upvoted and the site eventually only consists of the same bad one line jokes, completely devoid of content. At this point most of the old users move somewhere else.