Duplicate content is a fun topic in the SEO space because Google says don't worry about it because 30% of the web is duplicative. Google deals with it. But all good SEOs know, you don't want to have 5 pages all targeting the same keyword phrase because it is spreading you too thin.
In Google's Matt Cutts latest video, he talks about publishers who write several breaking stories on the same topic, that they can and maybe should use the canonical tag to clean it up and point the stories all to one main story when all is done and settled.
Listen to the video:
For publishers, that is really hard to do.
It is true, if you have the exact same story on multiple URLs, make sure your CMS handles the canonical tag for that. But if you have several writers covering the same story and it produces several similar stories on the same topic, that is hard to deal with. I guess it is best to have an editor consolidate the stories, but that is rare in the news publishing world.
Forum discussion at Twitter.