Google's Matt Cutts has put out a video talking about duplicate content. He was responding to the following user-submitted question:
Will multilingual translations of one [piece of] content across different websites attract [a] duplicate content penalty?
“The simple answer is no,” he says.
“The same content in English is different than the same content in French. So, if you had identical content in English, and then in English again, in theory, that’s duplicate content, and we might only want to return one copy of the English content. But if you have English here and French here, it’s really quite different.”
“Now, one thing to be aware about, is if you have written that content yourself - so you’ve written it for English, you’ve written it in French, or you’ve had it translated by hand for French, everything’s great. The world is good. Life is rosy. Be happy. But if what you’ve done is taken the English copy for your website, and thrown it into Google Translate, and done nothing more than auto-translate it into a bunch of different languages, that can be considered spamming, because in essence, it’s auto-generated. It hasn’t had a human’s eyes looking at it, figuring out what the idioms are, polishing it - that sort of thing.”
“So, I would recommend that if you have presence in 3 countries, to make sure that you have good content in those 3 countries, but don’t just throw it up in 38 or 40 countries, because you can translate automatically. Often, while Google Translate and other translate tools are much better than they were even a few years ago, there’s still a difference in quality between something that a truly skilled person working who speaks natively in that language, compared to just having it be done automatically.”
In another video earlier this year, Cutts discussed duplicate content concerns regarding blog posts on the home page:
Google recently started notifying webmasters when its algorithm selects external URLs for duplicate content via Webmaster Tools.