How does Google handle Duplicate Content?
Matt Cutts of Google states that about 25-30% of content on the net is duplicate and that it is not all spam.
Google looks for duplicate content and then tries to group it together and treat it as one piece. So when Google comes across two identical pages Google may decide to show just one of the pages on search results. Not all duplicate content is spam – it just needs to be clustered appropriately.
If all you do is duplicate content and you are doing it in an abusive, deceptive, malicious or manipulative way than expect Google to take action and treat your content as spam.