Spam and flame wars are not at all a new phenomenon.  The decline of intelligent conversation amidst the noise does seem pretty new.<p>I think this may be more related to the nature of these sites and the communities that form around them, rather than merely to the scale of the community.<p>Sites that go for a very broad appeal rather than targeting a specific, well-defined audience tend to have much lower-quality comments.  Engadget is a great example - it is a consumer-oriented tech blog, and it's structured more like a traditional publication than an online community.  The comments there are almost always not worth reading.<p>On the other hand, I visit sites like HN, Slashdot, and Ars Technica primarily for the discussions.