Twitter has started forcing users of the Tor anonymity network – along with serial trolls – to register their phone numbers, in order to stop abuse...Jim Killock, executive director of the Open Rights Group, has voiced concerns over the move. He said: “...[This requirement] could risk exposing people who have a legitimate need to keep their identity hidden – for example human rights activists, dissidents and victims of abuse..." ...[Twitter CEO Dick] Costolo has...said that he wishes not to impact on those using Twitter as a legitimate platform for dissent...