Cryptocurrencies have had a rough week: the value of bitcoin plunged to a mere 50 percent of its 2017 peak, and other currencies, such as Ethereum, Ripple, and Litecoin have seen double-digit losses compared to their heights from last year. Tuesday also witnessed the collapse of BitConnect, an anonymously operated crypto exchange that had been repeatedly accused of running a Ponzi scheme via its proprietary BCC currency.