"WordPress Translation Plugins" can cause your blog to be banned or penalized by Google and probably the other search engines, for spamming.
The plugins use the online translation engines like Google translators to auto-translate the pages. This is known as spam by google because the online auto-translators have a low quality and there is no human supervision on the translations. Also, these plugins translate the pages to over 70 different languages which is another spam. The only way to have your site in other languages is that you hire human translators to translate the pages by hand. Also, you should only cover the languages and countries that you offer your services to. You can not have your site/blog translated to 20 languages. See what Matt Cutts says:
I think you need to re-title this thread as your title is incorrect here. I've used a Google Translator plugin for sometime now with zero problems. This plugin is completely free, uses the Google translator, and doesn't actually create new pages..You simply press the icon for the flag you want, and the content is translated..no new content pages are made or anything of the like. Your thread should be titled "Copying Translated Content from Google Translator can Cause You a Penalty"..Once again, a WORDPRESS plugin will most likely NOT cause this..unless it actually making new pages where it's putting the newly translated content. Watch the video again and he explains it all in there. DON'T take your page, put it into Google Translate (NOT in Wordpress..just on Google Translates webpage) and then make a new page with that content on it. If your plugin just takes the current page and converts that page to the other language for the user temporarily it's no problem. Keep in mind, this is what MOST wordpress plugins will do. Google never sees the translated content, only the user who pushes the icon does.
This is exactly what I meant. I know those plugins that translate the pages after clicking on the flag have no problems, because the translated version sits on the user's screen temporarily will not be part of the blog.