While I have also noticed many duplicate articles, one way the community could try to avoid them would be by making sure that they are posting original sources (as suggested in the official guidelines), and not random blog posts (like the post a week ago).

edit: I have just noticed http://news.ycombinator.com/item?id=2777508 , which AFAIK links to the same URL as this.

Yeah, although sometimes it's not particularly obvious. I've noticed a lot of links to a site called http://ontwik.com/ being posted in the last few months (a Google search for ontwik on news.ycombinator.com shows over 100 results). It's a site that seems to take embeddable videos from YouTube, Vimeo and the like and turn them into pages like http://ontwik.com/html5-2/html5-games-with-rob-hawkes-of-moz... .. I can see why people are linking these things up, even though it should be the original YouTube video getting the link.

In terms of views, it did far better with this link than with the previous one. I was surprised, I only noticed when I looked it up on my analytics.

A big part of the problem is that it's abysmally hard to search for previous links on HN.

I think this might show that stories disappear from the front page too quickly -- although of course slowing that down would result in frequent visitors seeing less new material.

Or at the same times of the day but in different timezones.

Is that a bad thing?

That's a subjective judgment.

However, the window for even a popular link to remain on the front page nowadays continues to shrink. It's akin to the "attention span" of the site dropping. It has its pros and cons but shows that the system that fit the audience in a certain way in the past no longer does so (at least, it does not yield the same results).

My personal and subjective judgment is that this certainly becomes a bad thing at some point due to the lack of cohesion between users' experiences. Instead of a large share of the user base sharing a similar site wide experience, instead we only share knowledge within threads that we happen to see and participate in. There are, then, entire "shadow" discussions occurring in other threads that cover exactly the same topic. Fragmentation.