I am a big fan of using only Original content on your website. I believe that by only using original content you eventually will do a much better job with the search engines. In the last ten years the search engines have advanced a ton in their ability to not pull up the adsense scraper sites in the search engine results.
The days of the Machine Scraper sites are very limited. If your content is not original it will not rank in Google.
Here is a link from Wikipedia on User Gernerated Content:
The term user generated content entered mainstream usage during 2005 having arisen in web publishing and new media content production circles. Its use for a wide range of applications, including problem processing, news, gossip and research, reflects the expansion of media production through new technologies that are accessible and affordable to the general public. All digital media technologies are included, such as question-answer databases, digital video, blogging, podcasting, forums, review-sites, social networking, mobile phone photography and wikis. In addition to these technologies, user generated content may also employ a combination of open source, free software, and flexible licensing or related agreements to further reduce the barriers to collaboration, skill-building and discovery.