There are two reasons one is need and other is the ignorance that makes us vulnerable to scams like this. Facebook was considered more secure than other social networking sites, even the confidence of users increased when whatsapp privacy policy was launched.
But one thing is clear that we must not trust any app that will ask for permission to our mobile applications. Why they need it is first place? The answer is no,they don't!! Still they will ask us, and we trust them and provide our data.
Facebook is also doing same, now the data is displayed openly and so follows the applogies. Is seems impossible how the Facebook looked big firms are hacked and data is sent to third party like the Cambridge Analytica (the firm that claims the handling of Triumph election).
I think Facebook didn't do it deliberately but the one who did is Facebook.
We must keep our mind clear that before giving permission to anyone, why someone has need to access my phone or computer, if I can interpret it, he needs my data and behavior to suck my liquidity with one way or other.
Facebook may be regrettable but the phone call details that finished the human relations will not be trusted any more!
I think the race in compitition will never end and our online data will be never safe though facebook may now consider new security features, trust has been eroded to some extent.
I think the facebook must applogise to every user and must increase the security also if anyone is involved must be punished for the same. To gain the confidence of users facebook must update the encryption policy like whatsapp do.
Most of the people believe that the data was sold by Mark zukarberg, but I personally doesn't believe because why will he axe himself for a small gain which may lead facebook ruin with time. Hope facebook comes with a solution and produce the real picture of data leakage.