A little over a year after announcing mobile users can sign up for Facebook Messenger even if they don't have Facebook (FB) - Get Reportaccounts -- only a phone number is needed -- Mark Zuckerberg's company appears set to take another step towards making Messenger less dependent on Facebook's core services.

An "Add Contact" feature is being tested that lets users be added to a Messenger contact book without being added as Facebook friends.

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The logic behind such a move is pretty straight-forward: There are many people the average Messenger user might be interested in chatting or talking with at times whom he or she is uncomfortable becoming "friends" with on Facebook.

Making it easier to connect with such people should grow Messenger's social graph, increase its value as a networking tool and make the service more useful to non-Facebook users.

It also might not be a coincidence Facebook's test comes at a time when the amount of personal content being shared on its platform, such as status updates and uploaded photos, is believed to be under pressure. This has coincided with a surge in sharing on more private platforms such as Messenger, WhatsApp (also owned by Facebook) and Snapchat. Increasing the number of people a Messenger user can quickly share with could help Facebook grow its exposure to private sharing.

With a billion monthly active users (MAUs) as of last month, Messenger is now a massive platform in its own right, and one that Facebook is taking its first steps towards monetizing. It has also evolved from being a mere instant-messaging tool to a communications hub that supports voice and video calls, automated chatbot services and (in the case of the Android app) SMS messaging.

Maximizing the potential of such a communications hub means accepting that the connections it can support for a user can be very different from the ones supported by Facebook proper. And that Facebook's traditional social graph can't get in the way of fostering such connections.