Why do we care about falling prices?

Why should we care that prices are falling?  Isn’t it better for consumers to pay less for goods?  The prospect of deflation is so scary to economists and central banks alike, that it is causing the latter to pour trillions of dollars into their respective economies to prevent these drops in prices.  Just recently, the European Central Bank (ECB) pledged to buy government bonds as part of yet another quantitative easing to the tune of €1.1 trillion.  Many consumers do not understand the concept.  This is why everyone is concerned: