Robin Good: Andy Atkins-Krüger at Search Engine Land has written a very interesting and insightful report directed both at Google and at owners of multilingual websites which may have been affected by Google Panda.
According to the reasoning put forward in this article, there is a possibility that Google recent emphasis in requiring webmasters to adopt
the canonical and hreflang tags for multilingual websites may be a rather clumsy Panda fix.
"Canonicals and Hreflang tags are visible on the page to Panda and say “Please leave me in – I’m not just a duplicate and have a specific local market purpose and this is the market.”
"Many large websites rely on machine translation (not a good solution for SEO at any time) and they are particularly affected by Panda.
Google, if you disagree with me, please explain why all of this extra coding is suddenly needed."