In short, should you worry about having duplicate content on your site or not. The short answer, is no. Google's Matt Cutts said that if you have content that is duplicative in your site, don't worry about it. He said, "I wouldn't stress about this unless the content that you have duplicated is spammy or keyword stuffing."
He may have been specifically talking about boiler plate content like privacy policies and such. But he does expand his answer to tell you that the only real case you should worry about is when your using duplicate content in a spammy way.
Here is the video answer from Matt Cutts:
All this is to confuse people and make them think twice. They just want to minimize all the seo.
Never thought I'd hear him say that.
A misleading statement, why not to give full details, how to use duplicate content? Duplicate contents are allowed but what are necessary terms ?
Of course, answering a question on duplicate content in 2-3 minutes is not always the best idea.