A month ago, we reported an issue with fake rich snippets showing up more often in Google's search results. In short, some webmasters were faking their rich snippets and spamming Google with it.
While rich snippets are generated algorithmically, we do reserve the right to take manual action (e.g. disable rich snippets for a specific site) in cases where we see abuse, deception, or other actions that hurt the experience for our users.
If you do find such rich snippets that hurt the search quality, you can submit a spam report at this page.
Google asks you to fill out two things:
(1) The URL of the web page listed in the Google results and
(2) The search query you used when searching in Google.
So I guess now if you see rich snippet spam, you can report it to Google, if you want.
Forum discussion at Google+.