There seems to be a lot of stress on 'uniqueness' of articles. What is the reason that 'unique' articles are valued? Does google somehow realize that this is non-unique text (and rate it lower somehow), or is it simply that if someone searches for some keywords that are in the article, that now many sites (which use the same article) will appear? Following up on that, I'm wondering if anyone knows what constitutes a 'unique' article in google's eyes. I.e. if you wanted to change an article to make it unique, how many words would you have to change? Does structure matter?