Ravochol,
The deflation we have now is caused by defaults on loans by individuals, corporations and banks, so what’s wrong with it is partly obvious; it’s a symptom of wider economic pain, such as people not being able to pay their mortgages.
The point is that to a large degree this is due to malinvestment, which must be liquidated. As such, in this case, monetary deflation may be considered necessary. Even if you are a free banker, or an individual who believes that banks should increase liabilities to meet an increase in the demand for money, there would still be a necessary fall in the supply of money due to liquidation of loans caused by malinvestment.
More fundamentally, our money is created as debt issued at interest. The amount of money in the economy is equal to the outstanding debt.
This isn’t always true. For example, the Federal Reserve’s inflation of bank reserves is not debt, as banks are not liable to pay them back.
So if there are ten trillion dollars in the economy that have been issued at an average annual interest rate of 10%, then eleven trillion is owed back by the end of the year.
Well, all money isn’t created at once, so there’s no reason why all debt would have to be paid back “by the end of the year”.
Some defaults are ok, but too many and deflation can become a cycle - people default, there’s less money, forcing more defaults.
The causality is that malinvestment causes defaults. This “cycle” of monetary deflation ends when prices adapt to the new supply of money, returning profitability and readjusting the structure of production according to society’s time preference - as such, there is really no deflationary spiral.