<Snipped quote by Lmpkio>
That would be through IPs, but if the individual was using a proxy I wont make a difference.
As for contacting anyone, there's no one really. that's why spam is always a problem. Google provides a search engine, not a policing service.
If none of those ideas can help solve the problem, then WHAT can? Simply closing the site to a permanent lockdown, unable to allow any new members in? That would suck if it were the case.