The US Dollar is not the only currency out there that is losing value; in fact, all the world's governments are depreciating their currencies at alarming rates. Part of this is a desire to maintain competitive pricing with other countries, but most of it is just plain old politics. In order to provide more goodies to the voters, and to support the programs dear to their hearts, politicians have only three choices: take the money by force (taxation), create the money out of thin air (that is, to steal it through inflation) or borrow the money and pay it back later using one of the first two methods. Since high taxes crush productivity and shrink the economy, and borrowing only works while savers are willing to lend, it all comes back to money creation and inflation sooner or later.
As you can see, there is a "race to the bottom" going on. As policies change, and news reports highlight problems or gains in various countries, one currency can become stronger than another, and fall less or rise more. Later, the currencies may switch places. But over the course of time, the trend for all of them is clear, and it is not good.
Gold is the only currency that retains its value over long time periods. For thousands of years, many money systems have been tried by people all over the world, but only one has stood the test of time, over and over: Gold. There is nothing magical about it – it just works better than any alternative yet tried.
One of the key things that makes gold such a successful currency is that it takes real work to dig it out of the ground, refine it, and transport it to its ultimate users; as opposed to modern government currencies that can be created by typing an amount into a computer and hitting "enter". This keeps the amount of gold in the world growing at a very slow rate, ensuring that gold's value is stable.