"If you have a global site containing pages where the:
template (i.e. side navigation, footer) is machine-translated into various languages,
main content remains unchanged, creating largely duplicate pages,
and sometimes search results direct users to the wrong language, we’d like to help you better target your international/multilingual audience through: "

Informe o idioma para o Google, quando a navegação muda de idioma, sem que o conteúdo faça o mesmo, para evitar duplicação de conteúdo.

Como queria que o Google tivesse liberado isso há uns 2 anos…

link: Official Google Webmaster Central Blog: Unifying content under multilingual templates