A BBC investigation suggests companies are wasting large sums of money on adverts to gain “likes” from Facebook members who have no real interest in their products.
It also appears many account holders who click on the links have lied about their personal details.
A security expert has said some of the profiles appeared to be “fakes” run by computer programs to spread spam.
Facebook said it had “not seen evidence of a significant problem”.
"Likes" are highly valued by many leading brands’ marketing departments.
Once a user has clicked on a link the company it belongs to can then post content on their news feed, send them messages and alert their friends to the connection.
Facebook makes money by charging companies a fee to show adverts designed to attract new “likes”.
Some companies have attracted millions of “likes”.
But the BBC has been contacted by one marketing consultant who has warned clients to be wary of their value, and carried out an experiment that backed up his concerns.
The vast majority of Facebook’s revenues come from advertising and its performance will be scrutinised when it releases its financial results on 26 July - the first such report since its flotation.
Earlier this year Facebook revealed that about 5-6% of its 901 million users might be fake - representing up to 54 million profiles.
Graham Cluley of the security firm Sophos said this was a major problem.
"Spammers and malware authors can mass-produce false Facebook profiles to help them spread dangerous links and spam, and trick people into befriending them," he said.
"We know some of these accounts are run by computer software with one person puppeteering thousands of profiles from a single desk handing out commands such as: ‘like’ as many pages as you can to create a large community.
"I’m sure Facebook is trying to shut these down but it can be difficult to distinguish fake accounts from real ones."
A spokesman for the social network said: “We don’t see evidence of a ‘wave of likes’ coming from fake users or ‘obsessive clickers’.”
But Mr Cluley said it was in the firm’s interest to downplay the problem.
"They’re making money every time a business’s advert leads to a phoney Facebook fan," he said.
[ continue ]