Google has written two spam related posts over the Thanksgiving period on the Google Webmaster Central Blog tackling the issue of comment spam.
The first post focuses on the futility of comment spam, saying:
At best, a link spammer might spend hours doing spammy linkdrops which would count for little or nothing because Google is pretty good at devaluing these types of links. Think of all the more productive things one could do with that time and energy that would provide much more value for one’s site in the long run.
Those who may have been banned by promoting their sites through comment spamming are given advice. Site owners are also given advice on how to prevent comments spam. However, the post does not say that they’ll be penalized in some way if comment spam is present.
The second post talks more about using the fetch as Googlebot labs feature in Google Webmaster Tools to help detect if your site was hacked into. Often spammers will hack into sites that have vulnerabilities in order to inject malware, links or both into the site. They do this to artificially create links to their site, in order to help boost their Google rankings. Google wants to aid webmasters in detecting spam, discovering where it is on their site and then quickly remove it and patch the site in the future.