Over at the Mises Institute, Hans-Hermann Hoppe has a great article explaining why states create central banks and control the money supply. He reminds us that inflation always enriches those connected to the state at the expense of those who are not:
Rather, what the additional money you printed will affect is twofold. On the one hand, money prices will be higher than they would otherwise be, and the purchasing power per unit of money will be lower. In a word, the result will be inflation. More importantly, however, all the while the greater amount of money does not increase (or decrease) the total amount of presently existing social wealth (the total quantity of all goods in society), it redistributes the existing wealth in favor of you and your friends and acquaintances, i.e., those who get your money first. You and your friends are relatively enriched (own a larger part of the total social wealth) at the expense of impoverishing others (who as a result own less).
As they say, read the whole thing.