https://www.reuters.com/article/us-social-media-clubhouse/elon-musks-banter-with-robinhood-ceo-triggers-stampede-for-clubhouse-app-idUSKBN2A30R6 >A surprise chat between tech billionaire Elon Musk and Robinhood CEO Vlad Tenev on new audio-based social network Clubhouse has helped propel the app to the top of the startup charts and sparked a scramble for invitations to the exclusive service.