About two months ago, hedge fund billionaire Michael Novogratz made a bold announcement: He'd put 10% of his net worth into digital currencies including Bitcoin and Ethereum. But a lot can happen in a couple of months. Specifically, the price of Bitcoin has more than doubled, and the Ethereum price has multiplied six-fold. So around the time the cryptocurrencies reached all-time highs earlier in June, with the Bitcoin price hitting $3,000 and Ethereum breaking $400 the following day, Novogratz thought the current crypto boom had topped out. He sold "a bunch" of his digital coins. "I think the market had...