New accounts without an associated phone number tend to face a lock & challenge, for "suspicious activity" (even if they've never posted), which can only be reversed by adding a phone number.
So, Twitter is de facto requiring phone numbers on many more accounts than the initial sign-up flow might indicate – to the detriment of user privacy, & increasing the damage of compromises like this one.
So, Twitter is de facto requiring phone numbers on many more accounts than the initial sign-up flow might indicate – to the detriment of user privacy, & increasing the damage of compromises like this one.