Despite Google cracking down over the years on rich snippet spam and then applying rich snippet reductions recently - Google told a webmaster that the rich snippet spam didn't hurt their rankings.
A Google Webmaster Help thread has Google's Zineb explaining that while the site is faking their rich snippet reviews by showing users one thing and their markup containing something else - that action is not hurting their rankings. It is a breach of Google's rich snippet guidelines and thus may impact if and what rich snippets Google shows for the site.
But Googles Zineb said that is likely not the reason why the site doesn't rank well. The reason the site doesn't rank well is the "overall quality of your site," said Zineb.
Can having rich snippet spam hurt your rankings? I assume if it is really aggressive, yes but I assume that most violations will simply result in removal of rich snippets and not have a major impact on rankings. But then of course, sites spamming rich snippets are probably doing other tactics that are against Google's webmaster guidelines.
Forum discussion at Google Webmaster Help.
