Facebook has already established dominance as a social network, a private messaging client and a chatroom, so why not a telephone as well? Information about a developing app known as Phone accidentally leaked to Android users over the weekend, and indicates that Facebook probably wants a slice of the lucrative phone market.
Android Police reports (and this writer confirms) that on March 20, Facebook users on Android got an invitation to "Try Phone [FB-ONLY]" with a telephone icon next to it. (The icon looks suspiciously like the default phone icon on Android.)
Phone, the text suggested, could "[show] you info about who's calling and automatically [block] calls from commonly blocked numbers." Presumably, it would also connect via Facebook rather than a cell network, much like Messenger runs through Facebook's servers rather than a phone's SMS systems. This would make calls more difficult in areas without mobile data networks, but could also permit calls via Wi-Fi, like Skype.
The notification offered users the chance to install or upgrade the app, but the link led only to dead space, as the real app is probably still located on private Facebook servers. Whether this app will see full release or when everyday Internet denizens will get it is not yet clear.
Carrying voice signals across the Web is not free, and it will be interesting to see how Facebook monetizes the service. Users can't exactly look at ads while they're talking on the phone, so one must wonder whether Facebook plans to record conversations and transmit key words to third parties. Such a thing would not exactly be unprecedented.