Scraped content and empty directory pages (that washing machine reviews page that has nothing more than an H1 and some crummy auto-generated sentences) vs... Mediocre human written content from sites like e-How and other Demand media properties.
The first kind of content is pretty clearly spam, and doesn't deserve a place in the index. Everyone can agree on that, and I'm perplexed as to why Google hasn't taken more action against these types of sites. I have a hard time believing they can't do it algorithmically.
The second type isn't as clear cut. Most of the readers here and on the cited tech/search blogs know what this content is and where it comes from, and are probably a bit more critical of it than the average user for that very reason. I agree that these article directory pages are usually painfully mediocre, but I wonder if they aren't "good enough" from the point of view of someone who doesn't know better. After all, I havent seen much of an outcry about search quality coming from the mainstream; it seems limited to HN and other tech circles.