That thing facebook does with demanding your phone number, that's my favorite dark pattern. Apple does the same thing with iOS upgrades.
First you pose a seemingly innocent question, like 'would you like to give us your phone number so we can keep your account secure?' or 'would you like to upgrade to new iOS?'. Then you take away the NO option. You replace it with 'i'll decide later'. And by doing so, you make it not a choice for the user. You make it a statistical guarantee that sooner or later, most users will cave in and hit yes, even if by accident. iOS is an extreme example of this - when you say you don't want to upgrade, you are immediately prompted with a pin code request as if your device just locked itself, and your reflex is to punch in the pin to unlock it again. But if you read what it says at the bottom, it's asking for your pin to get permission to schedule the upgrade that you just said no to.
Whoever the designers are who came up with this stuff, fuck them. This shit is going to be in ethics textbooks in a decade or two. I hope someone from the facebook UX team is reading this, I hope they know their day job is to make the world a worse place.