Hello Michael,
This was a patent Google filed way back that was ratified this year. There is a news story on web pro news, I can't post it as I have not made enough posts but do a seatch for google similarity engine and you will find it.
It's positive news; it is the next stage on big G's war on scraper sites, copied articles are the like. Whether it becomes part of their algorithm, who knows.
We tend to advise our clients not to worry about the so called duplicate content filter, unless they are copying and pasting whole pages. Strangely, when we say this they often take another day or two to produce their content.
