We evaluate the spam report
We take spam reports very seriously, and we have dedicated staff to timely process reports.
We primarily evaluate spam reports in reference to our webmaster guidelines. We determine whether we agree or disagree with the user's report.
A spam site commonly uses illicit techniques to mislead search engines to (mis)lead users to certain websites. The Webmaster Guidelines cover most (but not all) common forms of behavior that we consider deceptive or manipulative. We suggest you review our webmaster guidelines listed in our Webmaster Help Center. These will help you create a search-engine friendly website that both Google and users would view as spam-free.
We take action on many confirmed spam sites, either manually and/or algorithmically. Furthermore, the extent of our action is dependent on the severity of the violation -- a confirmed spam report doesn't necessarily mean the entire site will be removed from the index.
If we believe that a reported spam site is in violation of the webmaster guidelines but is otherwise legitimate, we may try to contact the webmaster to correct their site. We contact webmasters via email and, if they have a verified site in Webmaster Tools, we can also send them a note through the Message Center.