Sites using other people's content, rss feeds and search engine results, are becoming very popular. They are called scraper sites.
Problematic of scraper sites
They are becoming a gigantic business. Sites with hundreds or thousands of optimized pages are generated and updated with no effort by shady webmasters.
Scraper sites are optimized to achieve top positions on search engines and drive as much traffic as possible to those sites. Traffic is monetized with cpc ads, like adsense, targeting high paying keywords.
A lot of programs are available to automatically assemble pages from content found on many sources. Many techniques are used to avoid search engines' filters.
New sites appear every day.
Scraper sites are a bad thing. They are becoming one of the most successful kinds of spam.