A few years ago Google's answer to duplicate content was simple: don't do it.
The site used to punish duplicate content by driving down SEO, but now that's not always the case. Google's current approach is more flexible and nuanced — duplicate content can even help you. Here are some examples.
Many of us use free online press release services to generate inbound links. Websites subscribe to these newswires and automatically display content that match keywords or categories they designate. A recent 4 Walls press release found its way onto dozens of sites; a search for the post title returned 67 matches, 34 of which were in Google's main index. The remaining 33 in the supplemental index were mostly sites that posted the release multiple times — the real duplicate content problem that Google is fighting in 2013.
4 Walls didn't just get lucky; the posting sites wouldn't publish press releases if they thought it sabotaged their search engine rankings.
Or consider an ILS feed, which often includes a 'romance' paragraph that's lengthy enough to trigger Google to think it's duplicate content. If duplicate content were an automatic SEO killer, ILS sites wouldn't show up in community searches. But they do, and all those individual community searches add up to a significant amount of free, inbound traffic for ILSs.
Original is always best, but if you follow some common-sense rules, duplicate content can work for you. Read Google's thoughts and guidelines here.