If you use rich snippets on your websites, you should be aware that Google is now penalizing websites for spamming structured data markup.
The new warning was first mentioned in a forum post on the Google Webmaster Central forums from a user who is asking for clarification about the warning and what the issue could be. It is a manual action penalty based on incorrect usage of markups, regardless of whether it was deliberate spam or simply a mistake.
The warning that would appear in a user’s accounts if they have manual action taken is:
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.
The writing on the wall for penalties related to rich snippets was back in October at Pubcon when Google's Matt Cutts talked about changes Google was planning in regards to rich snippets and dealing with related snippet spam.
Rich snippets could get a revamp and they will dial back on the number of websites that will be able to display rich snippets. “More reputable websites will get rich snippets while less reputable ones will see theirs removed,” says Matt.
The new penalty seems to affect websites that are misusing rich snippets, such as including authorship on homepages and reviews on pages where there are no reviews. But there was evidence that Google was attempting to educate webmasters on how to use it correctly when they made changes in December to add debugging support for structured data.
If you're unclear if you’re using rich snippets correctly, you should first check your Webmaster Tools account and see if there’s any issues that show up, either as issues or in the structured data debugging area. Google also has the pretty significant help area for rich snippets, including with videos, to help webmasters implement structured data correctly.