You must have heard "Content is King and It should be unique"
You must have heard "Search Engine Penalizes you for duplicate content"
So whats true and whats myth.
Search "Find a chiropractor that really suits your requirements and this can only be achieved by detailed analysis of different chiropractors. You can find a chiropractor to help you with your health problems." and you will get 9 results. It means google indexed 9 similar/duplicate articles. So its a myth that they penalize you for duplicate content.
Now question arises Out of this 9 which one will google consider when they show it in the Search Results. That will depend on the who has better links. So image you write a great writer/blog and someone copies it exactly and does great link building. Google will think their article deserves to be shown in the results and yours is just another copy. Scary isnt? But if your blog/website is reputed means you have good Page Rank, Google will favor you most of the times. So concentrate on reasonably Unique content, does not have to be absolutely unique and work hard on getting links.
Also its impossible for Google to index only unique content. They have to compare it to billion records before indexing, almost impossible to do that.
When Google talks about duplicate content penalty they are talking about duplicate content within the domain. Thats easy to catch and google does penalize you for that. Make sure you have unique titles, meta description, content for each of your page.
So focus on quality content (may not be completely unique) and quality link building.