It will be big help for companies which will be able to contact customers directly without any further effort. All these benefits can be used from other side too. Facebook users can contact companies for example like restaurants. Potential customer can ask about open hours and make reservation in one move without delays thanks to one app.
Of course it would not be Facebook if there wasn’t be space for commercials. Hello app has potential to cooperate with all Facebook platforms. So most likely script how the commercials on Hello will work is this. You find something you are interested in on Facebook and Hello will offer you phone call afterwards.