I agree with Marla Singer that social networks and ubiquitous commenting do encourage quantity rather than quality. Even on reputable newspapers' comment systems you often only get a lot of low-quality comments and little to no debate. And while occasionally insightful comments can be found on more quality-focused publications' comment systems, the times I've seen a useful comment on somewhere like YouTube could probably be counted on one hand. I can only think of one site where I routinely read the comments and gain insights from them, and it's a fairly quality-focused site to begin with, with a non-mass-market target audience.
Perhaps the comment-like, Web 2.0-ish system I've found most helpful personally is Stack Overflow. It's fundamentally a comment-like Q&A system, with a focus on quality and finding the "correct" answer, to the point that most topics that don't have an objective correct answer and locked or removed. Anyone can answer, and while not infallible, it really is a great resource for a programmer.
Arguably, the more advanced aspects of Web 2.0 that have had a more definitive positive impact. Things like Google Docs for collaborative document creation (and it's more cool when two people are simultaneously editing a document), interactive charts and documents on news sites, collaborative wikis with rich document-creating abilities for the workplace, and so forth. It's somewhat a question of how you define Web 2.0 as well. Are Internet radio and TV sites Web 2.0 since they would've been difficult or impossible to do well in the late '90s, or are they Web 1.0 since they generally don't have much active user interaction? If you define Web 2.0 by the technologies that allow more functionality, the advances are more compelling than if it's just user contribution.
If you define it by user contribution, there's also the question of what the cutoff is. CFC does allow a fair amount of user interaction, after all - forums, uploads/downloads, some degree of file storage, and, though poorly utilized, social groups and a Wiki. So is it Web 2.0, or Web 1.5? And there have been forums and BBSs long before CFC.
Still, many of the times I'm most fascinated with things on the Internet these days remain when I discover a Web 1.0 site that's a bastion of hidden in-depth knowledge. Other times it's exploring obscure corners of the Internet - finding some low-traffic FTP server with an abundance of old files straight from the '90s, for example. While I came to the Web too late to experience its early iterations, there's something satisfying about the uncommercialized, knowledge and sharing focus of those old sites.
And I'm okay with CFC being perpetually in 2007. That was when I joined the site, and it's a small comfort that it's almost the same now as it was then. True, it probably does need to change some over time to remain relevant, but as one of the few sites that's kept me coming back for 7+ years, it's doing something right as-is.
------------
Edit: I found another site like I mentioned in the second-to-last paragraph today, and nerd-sniped myself fairly well in the process. Went to dmoz.org and dug into their human-maintained web directory, since search engines aren't great at finding completely non-search-optimized old websites. Found a plain-old Web 1.0 HTML with no comment abilities nor JavaScript, nor I believe any CSS, but great content. Kept following links. Hard to beat a 15-year-old website about topics you're interested in, even if it does look like it's from 1999.