Can websites be penalized by search engines for using rich snippets spam, & if so, what are the consequences?

Absolutely, search engines like Google can and do penalize websites for engaging in rich snippets spam or markup spam tactics. Rich snippets are those enhanced search listings that display additional info like review ratings, prices, availability etc. While they can boost click-through rates when used properly, abusing rich snippets is considered a webspam by search engines.

If your site gets caught intentionally misusing markup to display misleading or irrelevant rich snippets, Google may hit you with a manual action penalty. This could mean your pages get downgraded in the rankings or even removed from the search results entirely.

At the very minimum, if Google detects rich snippets spam on your site, they'll simply remove those snippet enhancements from your listings. So you lose any potential CTR benefits you were going for.

Beyond that, the search engines may choose to algorithmically suppress the rankings of sites doing rich snippets spam as a way to discourage that kind of behaviour.

But it's not just about ranking penalties. Spamming rich snippets is a violation of Google's guidelines and provides a really poor experience for users. This could seriously damage the reputation and credibility of your site in the eyes of both users and search engines.

Some examples of rich snippet spam that could get you in trouble include marking up totally irrelevant content, using markup for fake products/reviews, or falsifying data like inflated ratings.

The best policy is to play by the rules - follow structured data guidelines and only mark up content that's directly relevant and 100% accurate on your pages. Trying to abuse rich snippets for short-term gains can potentially damage your traffic in the long run if you get caught.