Despite high-profile arrests and protocols with clever names, the robocall scourge remains indomitable. Wednesday, Federal Communications Commission chairman Ajit Pai teased a new proposal to put a serious dent in the problem. Stop us if you\u2019ve heard this one before. On the face of it, Pai\u2019s proposal sounds appealing. It would allow carriers to block robocalls by default, rather than on an opt-in basis.