Twitter has begun forcing Tor users to provide a phone number in order to verify their identity. The measure is to prevent that ill-intentioned would open a large number of new accounts to use for malicious activities. Twitter CEO Dick Costolo: “We suck at dealing with abuse and trolls on the platform and weve sucked at it for years” Twitter announced the adoption of a series of measures to eliminate harassment and any other behavior that violate company policies. Those used that will open a new account via Tor will have to provide their mobile number.”]
Source: https://securityaffairs.co/wordpress/34421/social-networks/twitter-locked-down-tor.html