There have been many episodes of mass hysteria in the past, sometimes they blow up and drop back down in the space of days, other times they keep going for years at a time. Cryptocurrency relies a large part of trust and simultaneously Bitcoin has been extremely volatile in recent history so it is a bit of a paradox. It seems to be a good short term tool for transferring good chunks of money around, potentially across borders, but due to it's instability it was never going to be a good long term investment. In some ways Bill Gates is right, for speculators they are only able to profit if the prices goes up between the time they buy and sell, otherwise they are destined to lose money as it doesn't produce anything in the meantime (unlike a company stock/share that pays out a portion of profits in different forms).