Silicon Valley Bank, the bank of choice for the venture capital and private equity crowd, is now the second-largest bank failure in U.S. history. Some $175 billion in deposits evaporated on Friday in what felt like the blink of an eye. It was an old-fashioned bank run for the modern age—an ugly combination of rising interest rates, some bad investment bets, and an inability to meet a sudden surge in withdrawals. “[M]eaning that as the tech sector freaked out about the solvency of its favorite bank, it didn’t have the cash on hand to pay them,” writes my colleague Tristan...