Google has started sending manual action messages to those sites which using fake Rich Snippets to game the Google results, they use mark-up language to fake rich snippets reviews, reputations which than shown by Google in search engine results.
In past, many webmasters have reported the Rich Snippets spam because it is easy to implement and Google has no such methods to verify its authority and authenticity. You can even show positive ratings and reviews about your product, services and website to fake Google by using mark up language. Many site owners used this to spam Google to gain higher rankings.
Google also announced Rich Snippet Spam report form to report such sites doing spam with fake snippets. Google asked to report search query and the page being returned in search engine results so that action can be taken.
Today, one webmaster reported in Webmaster Help Forum that he received such message from Google, the message contents are like
Spammy structured markup
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.
So if you have been gaming Google with false mark-up, you can also get similar message from Google