A post on Google Webmaster Central blog increases users awareness regarding webmaster practices that do or do not conform to Google's standards. This post was translated from their recently launched German blog.
The Google blog says: "Our spam report forms are provided in two different flavors: an authenticated form that requires registration in Webmaster Tools, and an unauthenticated form. Currently, we investigate every spam report from a registered user. Spam reports to the unauthenticated form are assessed in terms of impact, and a large fraction of those are reviewed as well.
So, the next time you can't help thinking that the ranking of a search result was not earned by virtue of its content and legitimate SEO, then it is the perfect moment for a spam report. Each of them can give us crucial information for the continual optimization of our search algorithms."
Google further clarifies certain FAQs. For a better insight read the complete post.