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However, the high-profile withdrawal of ads could lead to Facebook revisiting its advertising model, analysts said.

Henry Ellis, social media consultant at Tamar, the online advertising consultancy, said: "My guess is that Facebook will tell its advertisers that if they want greater control over where their ads appear it can do that for them, but that as a result, its costs and its advertising rates wil go up."

Companies are unlikely to ask to have their adverts on Facebook specifically, placing the matter in the hands of media buyers, who will buy set numbers of page views on several sites at once.

Facebook is expected to make more than $100 million (£50 million) in ad revenues this year but abounds with content that many advertisers may prefer to sidestep. Groups open for users of the site to join include "Thumbs up for leprosy" and "Americans for the death of Paris Hilton".

The company has spoken of itself as a potential $10 billion company, but has so far ruled out a sale and has said that it is unlikely to consider an IPO for 18 months.

A recent poll carried out by YouGov for Tamar found that two thirds of 18 to 35-year-olds in the UK use a social network. Two in five use two or more.

Eight out of ten users said they had “commented on or reviewed a brand or product on an online forum or social network”.

More than half of those polled said they would be put off a brand by negative comments posted on a social network, findings that have spurred brand owners to explore using the format in ad campaigns.

The perils of social networks for brand owners were further highlighted today when it emerged that 118 118, the directory inquiries firm, is investigating a Facebook page where its former workers trade insults about customers.

“The Survivors Of 118 118” page on the social networking site includes abuse about callers which claims to be posted by former employees of the service.

One message said: “I wrote a few a****** callers numbers on the walls of public toilets and pasted them on many an internet site.”

The company said that it was aware of the page and had launched an internal investigation.

“What we have ascertained is that nearly all the comments where we have been able to identify the identities have come from ex-employees. They absolutely do not represent the views and the attitudes of the vast majority of our staff,” it said.

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