Despite Google having a rich snippet spam form to report rich snippet spam to, Google's John Mueller said in a Google Webmaster Help thread that you can also let him know about spam and he will try to take care of it.
John said in the thread:
If you find more complicated cases that you can't easily fit into that form, feel free to send them to me directly through my Google+ profile ( http://google.com/+johnmueller ).
So, go ahead, use the form and John Mueller on Google+ to inform Google about rich snippet abuse.
This comes via the thread where John said testimonials are not reviews rich snippet worthy. And then people started reporting sites doing this.
Rich snippet spam is nothing new, it has been around since 2011. Basically since Google began fully supporting rich snippets.
Forum discussion at Google Webmaster Help.
