Prices actually going down all across the economy is an extremely rare phenomenon. It might had happen 100 years ago, in the age of precious metals, but people nowadays don't realistically expect prices to go down, and they don't "hoard" money in order to buy more stuff later. You might see it in some asset classes, say real estate, but not enough to cause a generalized and significant price drop in the whole economy.
What actually happens when deflationary expectations set in is not really a drop in prices, but a sharp drop in the velocity of money. It's intuitive: if the total monetary mass changes hands half often than it used to, the total economic output of the economy halves, even if prices stay the same. Because of the lower aggregate consumption, businesses start failing and credit becomes scarce. Mass unemployment and underemployment ensues. People start to consider themselves "lucky" to have a job at all, setting in motion the recessionary feedback loop: households and business defer consumption and investment because they anticipate "hard times" ahead, and holding onto their savings, preferably in the most liquid form possible, becomes an issue of survival. This reduces velocity further, in a self-fulfilling prophecy.
It important to underline that people don't deffer consumption for the sake of speculation, i.e "money will be worth more in the future". Most economic agents are risk averse and they hoard money to ensure continuity and survival, not to seek future profit. That's why simply injecting liquidity (preventing price deflation thus denying the future profit) does not solve the economic crisis. As governments around the world grudgingly start to realize, economic recovery is an issue of confidence, pure and simple. Unlike inflation, you can't manufacture confidence in the printing press - you need good policies and credible leaders.
Good point!
And , the deflation/inflation is not happening everywhere at the same time to everybody, especially with today's production model, some of enterprises can sit on tons of cash while others might be suffering long unemployment, commodities can have fast price rise while IT products keeps drop in price
So the current "one size fit all" monetary policy (e.g. either easing or tightening from top to bottom), when it solve problem in one part of the system, it will create problem in another part of the system. If the new money flow can directly injected into certain area which needed money most, then the whole situation can be controlled with much more flexibility and efficiency, and the regain of confidence is much quicker
For example, instead of inject money to buying underwater mortgage assets and save banks, put the money to jobless insurance program and ensure all the jobless people will have at least 10 years of jobless insurance, then the total consumption power of the nation will not change by too much, thus the economy will be easier to back on track
Someone might argue that these money will just be consumed and not generate any profit but that is a misconception, these money will surely generate profit for many enterprises which sold their products to those jobless people. It does not matter HOW money enter the system, but it does matter WHERE it enter the system