Just because Copyscape says there's duplicate content doesn't mean you copied from another website. My feeling is that when you're writing on a certain topic, you're naturally going to use some of the same words that appear on related websites. There are only so many words in the English language and we can't help but repeat them. Cite your sources and move on.
I totally agree, if copyscape has the ability to find some thing... The spun articles could not be published. But I see too many spun articles these days...
I've already explained this. Copyscape shingles down to 3 word matches. It's VERY hard to create ANY significant piece of text without using at least ONE three word shingle (e.g. 'I've already explained'). Copyscape will flag that up for you becuase *that's what its for - its a plagiarism detector, NOT a 'uniqueness' detector*. The search engine techniques are FAR more sophisticated. It's explained in more detail here - pass copyscape free and online