Duplicate content confuses search engines for a number of reasons. The algorithms running them have a difficult time differentiating between the different versions of a piece of content. This makes ranking the content difficult. Duplicate content causes more challenges when it comes to getting indexed. Because more than one copy of a piece exists, the search engine often doesn’t know which one needs to be indexed. Finally, the question of authority comes into play. If two or more versions of the content exist, the search engine is hard-pressed to figure out which version of the piece has greater importance.