Witnesses with opposing views on cryptocurrency and blockchain brought their opinions to a hearing in front of the U.S. Senate Committee on Banking, Housing, and Urban Affairs last Thursday in a bid to influence Congress’ thinking on the nascent technology.

Dr. Nouriel Roubini, a professor of economics and international business at New York University’s Stern School of Business, represented the staunchly anti-crypto and blockchain side, calling crypto the “mother and father of all scams and bubbles.” He cited scalability concerns, the centralization of mining power in non-U.S. countries and the environmental toll as problems with the industry’s growth.