The simple answer to this is no, it won’t. If your duplicated content is product descriptions then this will not harm your rankings. Although technically duplicate product descriptions should be penalised under the Panda update and Google’s new fresh content algorithm, they rarely are. If you have numerous product descriptions that are similar then you are more than likely using e-commerce or content management software to manage your website. If problems are experienced, then there are ways of restructuring your website to address these issues.
Remember that what Google is looking for are those people who excessively duplicate content, so a few pages on your site where the content is similar won’t really cause too much of a problem. However, if your website contains hundreds of thousands of pages with duplicate descriptions, it will. But hundreds and thousands of pages it will.
In many ways there are some potential advantages to creating unique product descriptions where possible. Our advice would certainly be not to use product descriptions that are worded in exactly the same way as competing websites. It’s much better if you can create product descriptions that are different, but this shouldn’t be attempted if it will impact on any otherwork carried out on the website.
If your site contains multiple pages with largely identical content, there are a number of ways you can indicate your preferred URL to Google. This process is called “canonicalisation”, and is explained on Google’s support pages: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=139066
If content is deliberately duplicated across domains in an attempt to manipulate search engine rankings or win more traffic, then Google will take action. Google sees such practices as deceptive and argues that they result in a poor user experience. Google’s algorithms are now predominantly geared to giving the user the best experience. Google aims to index pages with distinct and unique information, so if you’re running an affiliate site with lots of identical references that appear on dozens of other sites, then you may experience problems. Google’s advice in these instances is to make sure you add an original and unique angle so that your listings do not show up as duplications. If Google identifies instances where it feels the duplicated content is intended to manipulate the search engine rankings and deceive users, then it will make the appropriate adjustments in the indexing and ranking of the sites involved.