Messenger's new feature — Facebook's Vice President of Messaging, David Marcus, calls it "enhanced caller ID for messaging." — will also display information for Facebook Friends with whom you have not previously chatted with via the service. Thus users can avoid closing the circle on uninvited communications with friends...er, Friends with whom they would just rather not connect.
Regardless, though, of whether the shout-outs are coming from non-Friends or already-added Friends, Facebook will only offer ID information that is public or otherwise visible to the receiving user via the site.
In the same league as Hello, the Android-only caller ID app that Facebook introduced last month, Facebook is currently demonstrating a desire and direction towards facilitating the creation and expansion of personal connections between users who have common interests and concerns, regardless of whether they are strangers, acquaintances, or Friends (yet).
Previously, the Facebook Messenger service regularly handled messages from non-Friends by pushing them into the Other Inbox, of which the vast majority of Facebook users are not even aware. A workable solution for avoiding Nigeria-based monetary enquiries and offers to expand or lengthen usually-covered body parts, sure, but lousy in those less common but so-essential cases when a long-lost family member or friend is trying to reach out.
The new Facebook Messenger ID feature is currently rolling out to iOS and Android devices in the US, UK, France, and India.