Basically it's because our dollars are simply not worth as much as they were previously in relation to the currency of other nations.
This is caused by a variety of reasons (our huge trade imbalance is also key) but the bottom line is it's caused by our government spending more more than they take in. Then there are only two ways that they can finance their deficit spending: they can either borrow from other nations (this is mostly done by selling the debt to foreign nations) or they can print more money. The latter is also the main reason for inflation.
And that's exactly what the azzholes in Washington are doing at this very moment. They even spend ALL of the excess money taken in from current Social Security payments. They do this while pretending that they are concerned about the coming SS shortfall that is sure to occur. I would like just one time for the TV talking heads to ask these immoral jerks how they can pretend to be concerned about SS while basically stealing the curent excess funds being paid in to SS..
BTW, this is only going to get worse. MUCH worse. President Bush has not even tried to raise a single penny to pay for the Iraq war. It is possibly the only war in the history of the world to be funded by deficit spending. This is what can happen when we have a low IQ president who has probably never in his entire life paid a utility bill, a tax bill, or balanced his checkbook.
Then when all of the unfunded debt (that means the cost of future promised programs such as SS and healthcare and taking care of the Iraq vets) comes due and is factored in...coupled with when all those clever little foreign guys who are accumulating our debt decide they want to be paid...it will most likely result in a sort of chaotic economic perfect storm such as our nation has never before seen.
Goobers worry about terrorism. What they should be worrying about is the above.
But not to worry. As the scumbag politicians know very well, they will be long gone when this finally occurs and it will be our children and grandchildren who will be left to suffer and deal with it.
Sorry for the rant, but I think about this every time I see a politician carrying a bible or hear President Bush and his trademark "God bless America" bull*****.