David Marcus, head of Calibra at Facebook, testified before the U.S. Senate about the Libra digital currency project, emphasizing its aim to create a secure, low-cost global payment system. He highlighted the importance of thorough regulatory oversight before launch, a collaborative management structure through the Libra Association, and its potential to provide financial inclusion. The testimony also addressed consumer privacy, compliance with existing financial regulations, and the commitment to not utilize user data for advertising purposes.