The WordPress repository contains quite a few plug-ins that can automatically translate your blog’s content into multiple languages. Some of them will even store a copy of the translated text locally so subsequent requests for translated content are served directly from your blog.
Such plug-ins are popular for an obvious reason – they make your site multilingual with little or no effort and you can therefore possibly rank in non-English search engines as well (even with all the machine generated” content).
There are however two problems here. First, Google’s usage policy doesn’t allow other sites to store results of translation in the database for a long time so you are indirectly violating TOS because of that language plug-in.
The second and even bigger problem here is that instead of bringing in more search traffic, using language translation plug-ins can actually decrease traffic to your site because Google often views “auto-generated” pages as spam.
Xavier deMorales from the Google Search Quality team recently wrote on the Webmaster blog, very specifically, that websites should not serve machine translations to search engines.
We recommend that you do not allow automated translations to get indexed. Automated translations don’t always make sense and they could potentially be viewed as spam.
This is a very clear hint from Google and it applies to all language plug-ins that “cache” translated results for the purpose of making your site “multilingual” automatically.