A Facebook update will make users to become unwitting corporate ambassadors under plans by the company to allow the site’s main news feed to carry sponsorship messages carrying their mugshots.

Beginning in the New Year, so-called “sponsored stories” appear in the main news feed that Facebook users’ friends see. At present, if you click to “like” a product, it does not always appear in the main feed.

The new update will show friends your profile picture and the product you have “endorsed” in much larger form in the main news feed – a move that the site admits is designed to bring in advertising revenue.

Facebook say the scheme is a vital revenue booster, which will help it claw back some of the $1 billion a year it spends on developing the site.

Facebook claims that because the stories are labeled “Sponsored”, they will be less intrusive.

If a user decides to “Like” a product, the endorsement will also remain on their new, open “timeline” profile, enabling companies to pay Facebook to feature their adverts more visibly.

However, the announcement will infuriate users who feel that the social network is taking too much ownership over its 800milllion members’ personal information.

Facebook users in the U.S. have now launched a legal action against the company to contest the commercial use of the “Like” button.

A judge in San Jose, California, has allowed plaintiffs to bring a case against the social network in which they argue that the company is using their names and likenesses without their authorization.

Judge Lucy Koh dismissed an attempt by Facebook to have the case thrown out, saying: “In the same way that celebrities suffer economic harm when their likeness is misappropriated for another’s commercial gain without compensation, plaintiffs allege they have been injured by Facebook’s failure to compensate them for the use of their personal endorsement.”

The dispute centres on Facebook’s “Like” button, which allows users to virtually approve of a post by other users, or a product, with a single click.

These approvals then appear on that person’s profile page, and allow the social network to build up a profile of the user to target advertising.

The case will be heard next year.

Facebook said in an email statement: “We are reviewing the decision and continue to believe the case is without merit.”

The case comes after as a privacy watchdog set Facebook a 2012 deadline to change dozens of policies to improve users’ privacy.

Ireland’s privacy watchdog, the Data Protection Commissioner, audited Facebook’s international headquarters in Dublin and identified dozens of areas where the company needs to change the way it works.

The judgement will have implications for users throughout Europe and around the world – including changes to the site’s use of data harvested from users, and the need for clearer warnings about how users’ personal information might be used.