In response to the OP's original question around 'How Does google treat articles only some phrases are replaced'...
I have some experience here. I have been running an experiement in response to a plugin (wpeasycontent) which replaces block paragraphs in a duplicated piece of content.
In essence the thoery is you change the title of the article (lets say its a C&P from ezine) and add one to two paragraphs at the beginning and one to two at the end. You can either use a keyword targeted article or simply replace some of the terms with the keywords you are targeting.
Now, rather than buying yet another plugin I decided to test the theory manually. I copy and pasted 10 ezine articles and replaced the title with my keyword and added one paragraph at the start and one at the end.
Suprisingly all the articles (and I mean all) are ranking in the top 10, well above the original articles. I gave each article a reasonable sprinkle of backlinks (no more than 20-30 each) and within a few days were ranking well. 3 weeks later and they are still there.....
Its an interesting concept - I think the time it takes to whip up two paragraphs and a new title means the plugin is not really worth the outlay. However, a few simple changes made in this way clearly makes the content rank well even if it is not unique.
I have found that spun content (especially if it is badly spun) is easily detected as crap and doesnt rank anywhere whereas this method is great for visitors to your sites as the quality of content is good and sustains the reader long enough to click ads or see aff links etc and best of all it ranks.....
