Rich snippets and structured data markups can be an effective way of helping Google to understand the content on your website, and give your overall SEO a boost. However, if you use rich snippets on your website, you should be aware that Google is now penalizing websites for using these structured data markups incorrectly, or spamming the markups.
Google issues and informal warning about the misuse of structured data markups in a Google Webmaster forum post where a user requested clarification about the manual action penalty that showed up in their webmaster tools.
The warning that would appear in your webmaster tools if there is a misuse of markups on your site is as follows:
“Markup on some pages on this site appears to use techniques such as marking up content that is invisible to users, marking up irrelevant or misleading content, and/or other manipulative behavior that violates Google’s Rich Snippet Quality guidelines.”
This penalty may be enforces regardless of whether it was a simple mistake, or mislabeling in the structured data or if it was deliberate spam. So it is important when implementing your markups to ensure that all the information is correct and that you are using properly labeled markups.
If you’re unclear if you’re using rich snippets correctly, you should first check your Webmaster Tools account to see if there are any issues that show up pertaining to rich snippets and structured data. Google also provides a help area for rich snippets, that includes videos, to help webmasters implement structured data correctly.