But most important for me is the large volume of very interesting news that will not become "news." This is the kind of material that is more interesting than random pages but which lacks an appealing hook to place it on the front page of a magazine or even a news website. Often these items are timeless; they don't make the front page because they could be run at any time. But they are more valuable than odd curiosities. Because of the voting, tagging, bookmarking process enough people find the item worthwhile that they rise to notice.
I have encountered no other process in the world that is better at surfacing "news that stays news" and "news that will be news" better than these collaborative filtering sites.
Some of them provide a ranking of most popularly bookmark pages of the moment. I use this ranking function without bothering with the tagging part of sites.
The concept of "free" content producers, which I think WIRED called crowdsourcing, is going to be a short-lived joke. A loophole in the content business that will be closed by savvy startups which identify the top 5% of the audience and buy their time.