Facebook has begun a pilot program where users will be charged for sending each message on Facebook.

Facebook is the most visited website in the world. They published a press release on Thursday mentioning a "Small experiment" that will require users to pay a small sum if they want to contact persons they are not directly linked to.
Facebook Started Charging Some Users to Send Messages

Facebook says currently a small amount of people are testing out the pilot program and they are evaluating the data to see if the people are willing to pay the small fee or not.

Facebook says:

“For the receiver, this test allows them to hear from people who have an important message to send them,”
 In 2010, Facebook implemented a new feature where messages from unfamiliar people goes into others folder instead of inbox. So in this pilot program, some select individuals in the U.S. will have to pay a small sum if they want to contact persons they are not directly linked to.