This is the company that maintains a huge copy of the entire internet, and runs queries (including "is this site just a clone of another one?" type queries) on it, so on a technical level, they can probably do it. Of course, whether it's worth it to them to do so is another story.
That's definitely true, technically it could be done, similar to some plagiarism detection software used in academia to tell the level of similarities between publications. But I still think tweaking on the client side would be a more cost-efficient solution... but I agree, they are Google, they should always have free servers and cpu powers to throw in :)
