They did this only to cover their asses and that has been the only concern they've ever had. That they already tried to push the opt-in was of course only in fear of what just happened.
I'm sorry, I'm all for public apologies and I truly believe that it is in times like these companies have a chance to really prove themselves and really make a mishap something positive (and come out stronger than ever before). And they have tried to do that, for that I give them credit.
But. It was not a mistake. And this sentence really shows why: "Through the feedback we’ve received from all of you, we now understand that the way we had designed our ‘Add Friends’ feature was wrong."
They did it deliberately, there was not a mistake anywhere when implementing this nor with their intentions, and if they honestly didn't understand that what they did was wrong they don't deserve to be trusted again, not never. And if they did understand that it was unethical, which they undoubtedly did, it is even worse.
Their trust is not worth anything more than what they think they can get away with. The only thing that is different today from yesterday is that they think they can get away with less.
This desperately highlights why both android and iOS needs a way to spoof contacts for apps (return an empty list). Some android developers have solved this by having two apps in the market, one "private" version that requires fewer permissions. But that's a kludge (that I really appreciate) that almost noone uses.