Like all speculatory investments, which have little underlying value, the ride ends when the bubble bursts. Usually this happens when the money runs out - when

Like all speculatory investments, which have little underlying value, the ride ends when the bubble bursts. Usually this happens when the money runs out - when it's no longer possible to find the next "greater fool". That might take a while - there's a LOT of money in the world, and a lot of greedy people willing to be convinced that there's gold in them thar hills.