A Little Usage of Duplicate Content Won't Hurt Rankings

Duplicate content is always a concern for webmasters. Whether it's a website stealing content from another site, or perhaps a website that hasn't taken an active role in ensuring they get great unique quality content on their site, being duplicated out of the Google index is a problem.
In the latest webmaster help video from Google's Matt Cutts, he addresses how Google handles duplicate content, and when it can negatively impact your search rankings.
Cutts started by explaining what duplicate content is and why duplicate content isn't always a problem, especially when it comes to quoting parts of other web pages.

It's important to realize that if you look at content on the web, something like 25 or 30 percent of all of the web's content is duplicate content. … People will quote a paragraph of a blog and then link to the blog, that sort of thing. So it's not the case that every single time there's duplicate content it's spam, and if we made that assumption the changes that happened as a result would end up probably hurting our search quality rather than helping our search quality.

Source url : http://searchenginewatch.com/article/2319706/Googles-Matt-Cutts-A-Little-Duplicate-Content-Wont-Hurt-Your-Rankings