As I said in the investment email recently, a thing that sets cryptocurrencies apart from other flimsy investments is their ability to crash and then bounce back stronger than ever. Bitcoin has done it twice now. No other bubbly asset has ever done that before. It’s a sign cryptos deserve to be taken seriously — whether or not they’re your personal cup of tea.  Another reason to take cryptos seriously is the news last week a crypto exchange called Coinbase floated on the Nasdaq at a peak market capitalisation of $112 billion (why the Nasdaq, and not the New York…