Apple already has access to all the metrics that Facebook would be interested in. It seems to me like this is a set-up for Apple to force FB to buy the data directly from them.
Good. If they were doing it out of charity, a bit profit pressure, shareholder activism or change in management and the move is reversed. Being grounded in sound business logic and self-interest makes me trust it.
I just think that a significant number of people will see what they're doing and thing "Oh, they're looking out for me." I think it's best to be skeptical of any company's motives, whether their current business decisions seem to help their users or not.
It's possible that they have no intent to do so, but a corporation's primary interest is making profit. And what would be a simple, yet significant, source of new revenue? Selling user data.