The world relies on the U.S. Dollar to price many of its good, so when the dollar experiences a steep drop in value people start to notice! You see, when the dollar weakens, commodities priced in dollars become cheaper for buyers holding other currencies. This causes an increase in demand that in turn causes the prices of commodities to rise since they are getting paid in less-valuable dollars. This pressure of rising prices has forced many central banks to allow their currency prices to appreciate against the dollar. Obviously, this is a big problem for the dollar which then faces increased scrutiny.

From the Wall Street Journal:
A rising tide of inflation pressure around the globe is putting more stress on the beleaguered U.S. dollar, as central banks from China to Chile fight rising prices by letting their currencies strengthen ... One big source of inflation worries: soaring prices for raw materials. Yesterday, oil closed at a new high of $107.90 a barrel on the New York Mercantile Exchange, jumping $2.75, or 2.6% as more investors piled into the hottest commodity around. Oil's rise is fueling gasoline prices: The average U.S. retail price of a gallon of regular gas rose 6.3 cents to a new high of $3.225 this week, the U.S. Energy Information Administration said yesterday.