Mozilla.org was slapped by Google with a manual penalty for “user-generated spam”. You can read more details here.
1) You can never be too big to fail – Even sites like Mozilla can be a target of spammy links from comments. Even though you’d think that a popular site like this would have enough natural links to outweigh a potentially negative attack, it can still happen.
2) Spammy tactics can hurt your website and brand – You need to monitor your site and check Webmaster Tools for messages about unnatural links, detected malware, increase in errors and more.
Prevention is the key to being attack and active monitoring can help keep your site in top health. You wouldn’t want your website to be associated with payday loans or generic medications, right?
3) A site can receive different types of penalties – Whether it’s intentional (like JCPenney or even Chrome) or unintentional, like the case with Mozilla, Google is ready to give out appropriate penalties. In this case, Mozilla didn’t receive a “full” penalty but rather, had penalties for pages where there were spammy comments.
4) Ask for help – The Webmaster Portion of Google Product Forums is a great place to ask for help and suggestions from other webmasters. Although we all won’t be as lucky to receive immediate and direct comments from John Mueller or Matt Cutts, there are a lot of helpful tips you can receive from outside people who aren’t biased and naive about your site/industry.