What happens if people expect that, in the future, the money-supply growth rate will increase to ever-higher rates? The demand for money would, sooner or later, collapse. Such an expectation would lead (relatively quickly) to a point at which no one would be willing to hold any money as people would expect money to lose its purchasing power altogether. People would start fleeing out of money entirely. This is what Mises termed a crack-up boom:[2]
If once public opinion is convinced that the increase in the quantity of money will continue and never come to an end, and that consequently the prices of all commodities and services will not cease to rise, everybody becomes eager to buy as much as possible and to restrict his cash holding to a minimum size. For under these circumstances the regular costs incurred by holding cash are increased by the losses caused by the progressive fall in purchasing power. The advantages of holding cash must be paid for by sacrifices which are deemed unreasonably burdensome. This phenomenon was, in the great European inflations of the 'twenties, called flight into real goods (Flucht in die Sachwerte) or crack-up boom (Katastrophenhausse). Everybody is anxious to swap his money against "real" goods, no matter whether he needs them or not, no matter how much money he has to pay for them. Within a very short time, within a few weeks or even days, the things which were used as money are no longer used as media of exchange. They become scrap paper. Nobody wants to give away anything against them.[4]
See:
http://wiki.mises.org/wiki/Hyperinflation