digg.com
I hate reading the comments people make about the articles. Well, to be more precise, I hate that I have to wade through a sea of useless / ill-informed comments before I get to an informed statement. Of course, there is no guarantee that an insightful comment will accompany any given article, but usually you'll find something worthwhile.
Still, the crap-to-quality ratio at digg is absolutely horrendous. Why read the comments, then, you ask? Well, an insightful comment will put the orginal article in context, which is especially useful if you aren't familiar with the topic at hand.
It's really pathetic -- most folks don't even read the article. Of those that do actually read (or rather, skim) the actual article, their reading comprehension is often abysmal.
Slashdot contributors, to their credit, seem to be slightly more interested in furthering the discussion with informed comments. Of course, Slashdot still suffers from idiots, but the crap-to-quality ratio at slashdot is slightly better than that of digg.com
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Don't even get me started on the countless idiots who use sensational headlines to draw attention to the articles they submit. Or how ill-informed these story submissions are themselves.
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Yes, I used a sensational headline myself, just to get you to read this. Sorry. I actually like slashdot and digg a lot.