Before Google cracked down, there were a whole bunch of low-quality "vertical search" and "price comparison" sites that rendered Google basically unusable for certain kinds of searches by spamming the results with page after page of highly SEO optimized information-free placeholders stuffed with ads. Their business model was basically to make money by making everyone's search experiences worse, hoping enough people would get desperate enough to click on one of the ads in a futile attempt to get what they were looking for. That's why Google's crackdown hurt so many vertical search/price comparison sites so much; they had no organic non-Google-sourced traffic because no-one wanted to go back there.