The supply of coins grows at the same rate regardless of demand. Stability requires a flexible supply increase to correspond with demand increase. This limitation will be an impediment to the growth of Bitcoin commerce.
Your logic is the product of living under an inflationary economic system with a gaping security hole.
The truth is that economic stability is higher under an inflexible money supply. This is also the case historically when one considers the stability created e.g. in the 19th century under a relatively fixed quantity of physical specie.
The increase in stability is because demand increase (or decrease) will meet market forces and equilibrium can be reached. Manipulation of the money supply only hinders the ability of the free market to respond to changes, especially when the exact amount of the manipulation is kept secret from market participants. The only limitation caused by an open money supply is a limitation on inflationary fraud.
Oh, I'm completely against inflationism in traditional banking. What I mean is that with gold, for example, an increase in demand will lead to an increase in gold mining, which increases the supply to match. With Bitcoin, supply is increased at the same rate regardless of demand so no equilibrium price can be sustained.
I'm not talking about having some centralized jerk manipulating the supply to his liking, but rather having a dynamic market instead of a static one.