Facebook users are to face charges if they want to message people outside of their social network.
The social networking site is planning to charge users up to £10 if they contact people who are not "friends" or friends of "friends" -- with the cost rising depending on how famous their target is.
The cost of an individual message could be as little as 70p to ordinary Facebook users but could rise to £10 for celebrities. Facebook says it is introducing the payments to prevent spam being sent to users of the network.
The fee structure will reportedly be decided by a mathematical formula that takes into account a number of factors, including the number of followers a user has on Facebook and how many messages they receive.
But social media commentators have expressed concerns that the charges are only the beginning of a pattern of using such web services as a source of revenue.
Facebook has always boasted that the site is "free and always will be."
For the moment, users can message anyone who uses the website for free but, if these charges are introduced, users will have to pay if they want to message people who are not friends or friends of friends.
Messages to non-friends will go to an alternative message box and be treated as spam. When a user decides to accept the fee, they are requested to pay immediately using a debit or credit card.
However, the company dropped a scheme allowing users to pay $100 to contact celebrities, including Facebook founder Mark Zuckerberg.
"The system of paying to message non-friends in their inbox is to prevent spam while acknowledging that sometimes you might want to hear from people outside your immediate social circle," Facebook said.
"We are testing a number of price points in the UK and other countries to establish the optimal fee that signals importance. Part of that test involves charging higher amounts for public figures, based on the number of followers they have.
"This is still a test and these prices are not set in stone."
The cost of messaging a celebrity will vary according to their popularity and is bound to become an instant measuring tool between the famous and the wannabes.
The scheme has already been tested in the United States.
Facebook began charging users on a pilot basis in the US in December last year and has decided to begin rolling out the system on a global scale.