Using rich snippets on your website is something that can earn you a penalty from Google, according to a post written on the Google Webmaster Central forums.
It seems that a user queried a warning he’d received and was told it was given for a manual action penalty, levied against his site due to his incorrect use of markups.
Rich snippets are designed to summarise the content of a web page, making it easier for users to understand what the page is about in Google's search results. Google advises that “if you're considering taking advantage of rich snippets, think abut whether a user would find the information helpful when choosing between search results.”
Google penalises techniques that are used by companies who use rich snippet spam, including marking up content that is invisible to users, marking up misleading content and other disingenuous practices that violate the Google Rich Snippet Quality guidelines.
The new practice of penalising rich snippets that have obviously been manipulated by spammers, may well lead to them only being available for reputable websites, while less reputable sites are stripped of theirs. Check your Webmaster Tools account to make sure you're in the SEO clear.