Would it really help with spam though? The rewards for a spammer to make it to the first, second, or even third page are probably worth the risk of negative karma.

As for duplicate articles, I'm not even really sure what the problem is. Is it duplicate articles (same url, slightly different) that clog up the system? Or is it the same subject being covered from many different sources? There have also been a few times within the last month where two stories about the same topic will be right next to each other on the front page--amazon/apple/other big industry announcements like to do this.