Facebook describes the move as a "a small experiment to test the usefulness of economic signals to determine relevance." That experiment will charge users money to directly message people they're not friends with, LinkedIn-style. For $1 these users who have no connection to you will get their messages bumped from the veritable spam folder that is your Messages box "Other" tab (pictured above) over to the precious Inbox. Of course, you might not have ever recognized the "Other" section, but a Facebook spokesperson once explained it to The Atlantic Wire this way: "By default, messages from friends or friends of friends go into your Inbox. Everything else goes to your Other folder."
There are a lot of potential problems with this, of course. From the recipient end, "Facebook is selling access to your inbox," as AllThingsD's Peter Kafka put it. And on the senders end, the social network is creating a social hierarchy, where those willing to pay a premium can reach anyone they want, kind of like HR recruiters, or desperate job hunters, pay up on LinkedIn. Kafka, of course, has a rosier perspective: "Maybe you do want to hear from those people! And the one-message-a-week cap, combined with the $1 fee, will prevent your inbox from filling up with spam." But it's hard not to imagine how the move might elicit more spam. Instead of messages from unwanted humans getting filtered off into "other," your more intimate inbox will start filling up. And so what if you want to send a message to a random person asking them a question? That used to be free! But not in 2012, the year Facebook tried to make money off everything. Not at all.