The feature is being tested out on US users first and allows them to send a message to a non-friend for $1.
Mark Keenan, of Divorce-Online, thinks the new service could "spell disaster" for online dating sites, including those aimed at people looking for affairs.
However, as a divorce specialist, he's more concerned that the additional feature together with Facebook's new Graph Search engine could lead to the social networking site becoming a factor in more relationship breakdowns.
In fact, surveys by Divorce-Online in 2009 and 2011 found that Facebook had been mentioned in a third of the divorce petitions handled by the UK-based company.
The new Graph Search function allows users to connect with other users who have similar interests and make new friends.
While many of the connections will probably be innocent, Keenan fears the search engine may be exploited by "bored married people looking for illicit fun".
"We have continued to monitor the divorce petitions we produce and the prevalence of the word Facebook in them has if anything slightly increased," he says.
"[Facebook] has become the all pervasive tool for communicating in affairs, replacing e-mail, texting and phoning."