Google's John Mueller said in black and white in a Google Webmaster Help thread that using Google Translate to translate your whole site, is the same thing as "auto-generated content."
This should come to no surprise to anyone here. In fact, the first time Google came out on this was back in August 2010 and then it became really official when Matt Cutts released a video on the this topic on March 2011.
If you read the content guidelines section on automatically generated content, it spells it out there too saying:
Text translated by an automated tool without human review or curation before publishing
Trust me, a few years ago, this was not seen as a spam tactic.
Here is Matt's video:
John, in the thread mentioned above, responded with concern about the translation on the site. John said:
I don't know if others have mentioned it, but the translations on your site appear to be very bad. Keep in mind that automatic translations are seen as auto-generated content from our point of view, and should be blocked from crawling / indexing.
Forum discussion at Google Webmaster Help.