In a recent video by Matt Cutts , he has shared that there is almost 25%-30% of duplicate content on web and Google does not consider all of it a spam. Having read that, it is important for you to know what he further clarifies in the video:
How Google treats duplicate content?
Since there is more than one fourth of content on web that matches each other in some way, Google does not discard all of it. It clusters all the identical pieces of content in one group and treats it as one. In search engine results, Google shows any one of this cluster, whichever is better than all. It’s about giving the right rank to right content. Hence, the rest of pieces of a cluster would be shown somewhere very down in SERPs.
When would Google consider your content as spam?
Uncovering the truth behind it, Matt said that although Google reserves the right to take action against abusive, malicious or deceptive ways of creating duplicate content but there are few cases where duplicity is not punishable. For instance, things like terms and conditions of various companies are similar and Google does not take any action against it. Hence, the bottom line is that if you are adding some value to search then you may not be spammed.
The crux of what Google’s Matt Cutts has told in this video is that your content must be made for people and not for search engines. It is the prime point in Google Webmasters guidelines too, so you need not be troubled,until your content is offering an experience to users and adding some value to search.