The launch of U.S. exchange-traded funds (ETFs) tracking bitcoin deepens ties between the volatile world of cryptocurrencies and the traditional financial system, potentially creating unforeseen new risks, some experts say. The Securities and Exchange Commission (SEC) this month approved 11 spot bitcoin ETFs from issuers including BlackRock and Invesco/Galaxy Digital, in a watershed moment for a crypto industry dogged by bankruptcies and crime. The SEC had long rejected the products citing investor protection concerns, but was forced to rethink its position after losing a court challenge brought by Grayscale Investments.