Well he's an idiot for starters. Using a subdomain won't get him any ranking or SERPS ... major penalty for subdomains.
If hes registered at GoDaddy... then go through the Domains by Proxy service (
http://domainsbyproxy.com/LegalAgreement.aspx?prog_id=). They will get a hold of him and charge him for relaying the message as well - I think it's $35 bucks per e-mail.