It creates artifical inflation. The dollar is no longer backed by gold or silver, hasn't been for a while. Money is basically a "trust" concept. You used to barter (1 cow for 10 hens). The idea of money is that 1 dollar will buy both, so now I don't need to trade you a cow for a hen. I can sell my cow for a dollar and pay you a dollar for the hen. We all trust that a dollar to me is the same as a dollar to you.. By introducting fake money, there is no real expectation of value (a cow or a hen) so it makes everything worth additional money. The person with the hen anticipated me having 1 dollar (from my cow), but now I have 2 dollars (one real from my cow and one fake from my basement). The hen owner will change their value and prices accordingly. Or worse, I kept my cow and produced that one dollar in my basement and buy your hen. Now I have a cow and a hen, and nobody else has anything except for fake money.. . Fortunately, money circulates through banks so often, that counterfeit money is caught and removed from circulation.