I’ve been following the discussion about Google and mirrored information for some time. It is “common knowledge” that Google penalizes page rank when it determines that content is duplicated somewhere else. In fact, I’ve read many experts stating that there should be no duplicate domain names and no duplicate content anywhere.
On the face of it the arguments appear to be sound. Google obviously has several billion pages in it’s database and could, it appears, easily determine if content is duplicated. It also seems, again on the face of it, that it’s reasonable to check for duplicate content, as this is the “mark of a spammer” and not necessary on the web with hyperlinking available. At least, this is the common wisdom.