This sort of thing was mentioned in an early talk given by someone at Google Translate. (Sorry, I have neither the link nor the name of the person handy.)

As it makes use of parallel corpora, there were examples of documents mentioning (say) a famous person in the United States, but when the document was manually translated into French, the human translator selected a different famous person more well-known in France. It made perfect sense in the context of the document, but it threw a wrench into the automated translation based on those documents.