The US Customs and Border Protection agency has submitted a request to the Office of Management and Budget asking for permission to collect travelers social media account names as they enter the country. The public and affected agencies are asked to comment on the request within 60 days of its publication (i.e until August 22, 2016), but haven t offered an online form for comments to be submitted. The question, if the request passes, is optional for now, but this is the perfect stepping stone for making answering that question mandatory in the future.
Source: https://www.helpnetsecurity.com/2016/06/27/us-customs-social-media-account-names/