Lots of websites make it to the top search engine rankings because of the right combination of effective SEO techniques and hard work. It makes sense having search engine optimized pages blended with functional web content. By doing so, the site is given more chances to rank high in search engine result pages (SERPs)

But there are also those that enjoy improved search engine rankings by having scraped or autogenerated web pages. This method is based on the false theory that multiplying web pages with irrelevant and random content is part of ideal SEO techniques. These techniques are done by scraping content from sources known for good, valid content such as the Wikipedia and the Open Directory Project, or by abusing qlweb style catalogues.

This is what Google has to say:

Google is willing to take action against domains that try to rank more highly by just showing scraped or other autogenerated pages that don't add any value to users. Companies, webmasters, and domain owners who consider SEO consultation should take care not to spend time on methods which will not have worthwhile long-term results. Choosing the right SEO consultant requires in-depth background research, and their reputation and past work should be important factors in your decision.