Susan Moskwa has posted an article demystifying the “duplicate content penalty” discussing — “there’re some penalties that’re related to the idea of having the same content as another site. Check Webmaster Guidelines:

• Don't create multiple pages, subdomains, or domains with substantially duplicate content.
• Avoid... "cookie cutter" approaches such as affiliate programs with little or no original content.
• If your site participates in an affiliate program, make sure that your site adds value. Provide unique and relevant content that gives users a reason to visit your site first.

He says most site owners aren't talking about scraping or domain farms; they're talking about things like having multiple URLs on the same domain that point to the same content. Like www.example.com/skates.asp?color=black&brand=riedell and www.example.com/skates.asp?brand=riedell&color=black. Having this type of duplicate content on your site can potentially affect your site's performance, but it doesn't cause penalties. Refer this article on duplicate content.

Full Article