I think Digg could possibly run into the problem of poor or mediocre content because the top users were so committed to seeking out unique content. It's not that others can't or won't, it's just that I'm not sure they will put in as much effort on a consistent basis. I haven't really heard what top diggers are saying about this, but I imagine some of them are a little insulted that they're not going to be recognized for their effort and just leave all together. Some of them have been on the verge of leaving Digg for a while now.
I definitely agree, a story should be Dugg based upon the story itself, but I'm just curious if/how the quality of content will change.