A US judge has ordered a self-crowned "Spam King" to pay Facebook 711 million dollars for slipping uninvited into people's accounts to send bogus marketing messages.

Facebook on Friday acknowledged that Sanford Wallace is unlikely to pay the money awarded by the court but proclaimed the ruling a blow in an ongoing battle against spam at the leading online social-networking service.

"While we don't expect to receive the vast majority of the award, we hope that this will act as a continued deterrent against these criminals," Sam O'Rourke of the Facebook legal team said in a blog post announcing the ruling.

"This is another important victory in our fight against spam. We will continue to pursue damages against other spammers."

The federal judge in the Silicon Valley city of San Jose also referred the case to the US Attorney's Office, asking prosecutors there to pursue criminal charges of contempt against Wallace.

Wallace, who has filed for bankruptcy protection in US courts, might be able to dodge paying Facebook damages awarded in the civil suit but a criminal case would expose him to the possibility of spending time in jail.

Facebook filed its civil suit against Wallace and his business partners early this year.

In court paperwork, Facebook described Sanford as "a notorious Internet scam artist who has been involved in various illegal spamming and malware activities since the mid-1990s."

MySpace last year won a 230 million dollar judgment against Wallace and accused collaborators for spreading porn and gambling spam at the News Corp-owned online social networking service.

Wallace has reportedly promoted himself as an original "Spam King" during his career as an Internet marketer.