SAN FRANCISCO (REUTERS) - Child rights advocates tried to convince a United States (US) judge on Friday that a Facebook legal settlement did not go far enough to keep content created by minors out of the hands of advertisers.

Five plaintiffs filed a proposed class action against Facebook in 2011, saying the social networking giant's "Sponsored Stories" program shared user's "likes" of certain advertisers without paying them or allowing them to opt out.

The case has highlighted tension between privacy concerns and Facebook's drive to monetise user content.

Under the terms of a proposed settlement, Facebook will pay US$20 million (S$25.4 million) to compensate class members, and promised to give users more control over how their content is shared - changes which plaintiff lawyers estimate to be worth up to US$145 million.

Facebook charged advertisers nearly US$234 million for Sponsored Stories between January 2011 and August 2012, court filings show.

US District Judge Richard Seeborg in San Francisco preliminarily approved the settlement last year, but he still must give it a final sign-off.

At a hearing on Friday, Children's Advocacy Institute attorney Robert Fellmeth told Seeborg that no minors should have their content shared with advertisers. Seeborg did not say how he would rule, but said his role is only to say if the settlement is fair.

"My function here is not to craft the perfect policy for minors," Mr Seeborg said.

Earlier this month, Facebook announced a retooling of its advertising product offerings and eliminated the term "Sponsored Stories", though the company can still share its members likes of different products. Facebook attorney Michael Rhodes said in court on Friday that the legal settlement would still cover those types of advertising practices.

Under the deal, impacted Facebook users can claim a cash payment of around US$10 each to be paid from the settlement fund, and plaintiff lawyers are seeking US$7.5 million in fees. Any money remaining would then go to charity.

Mr Seeborg called the US$145 million valuation of changes to Facebook's site "highly speculative." However, plaintiff lawyer Robert Arns said the changes were very significant. "We think it sets a new standard for all social media sites in the US,"Mr Arns said.