Google’s John Mueller said again that any type of bad content on your site, be it content you write yourself or content published by users – i.e. user generated content, can be used to judge your site. He said the content displayed is what Google uses “for your website’s crawling, indexing, and ranking.” John said this on Twitter: In fact, just a year or so ago, Google gave us tips on blocking spammy user generated content. John Mueller has been addressing these topics since before 2011. So be careful about not just your quality of writing but anyone else who can write on your site. Forum discussion at Twitter.