Hi @pfunk - it's more like a scanning tool. Here is a link to their FAQ page. http://www.copyscape.com/faqs.php
I personally use the premium service for scanning my own material or researching an article that I believe is plagiarized. It does not differentiate between which is original or copied, or whether there are proper citations to the copy. For the individual, it's a great tool to protect one's own material. They also have a copyscape sentry tool, which will scan the entire web weekly or daily for duplicate copies of your material, which could be costly.

I would personally love it if Steemit was able to implement something like an opt-in (for a small fee) where everyone could enter their text and scan it on site before hitting the post button. Perhaps with an automatic banner that states it is plagiarism free or a Trusted contributor.