Empires - Economic reasons for building them; why they ultimately crumble

The below exerpt from a speech served as a history lesson for me about empires.

The speech was by Ron Paul in 2006 and focuses on the Dollar Hegemony and why it will end -
"The End of Dollar Hegemony" - http://www.house.gov/paul/congrec/congrec2006/cr021506.htm
Video Link - http://video.google.com/videoplay?docid=-8327695139643041382#

Excerpt explains why empires were built, and why every empire ultimately ended -

First it was simply barter of goods. Then it was discovered that gold held a universal attraction, and was a convenient substitute for more cumbersome barter transactions. Not only did gold facilitate exchange of goods and services, it served as a store of value for those who wanted to save for a rainy day.

Though money developed naturally in the marketplace, as governments grew in power they assumed monopoly control over money. Sometimes governments succeeded in guaranteeing the quality and purity of gold, but in time governments learned to outspend their revenues. New or higher taxes always incurred the disapproval of the people, so it wasn’t long before Kings and Caesars learned how to inflate their currencies by reducing the amount of gold in each coin – always hoping their subjects wouldn’t discover the fraud. But the people always did, and they strenuously objected.

This helped pressure leaders to seek more gold by conquering other nations. The people became accustomed to living beyond their means, and enjoyed the circuses and bread. Financing extravagances by conquering foreign lands seemed a logical alternative to working harder and producing more. Besides, conquering nations not only brought home gold, they brought home slaves as well. Taxing the people in conquered territories also provided an incentive to build empires. This system of government worked well for a while, but the moral decline of the people led to an unwillingness to produce for themselves. There was a limit to the number of countries that could be sacked for their wealth, and this always brought empires to an end. When gold no longer could be obtained, their military might crumbled. In those days those who held the gold truly wrote the rules and lived well.

That general rule has held fast throughout the ages. When gold was used, and the rules protected honest commerce, productive nations thrived. Whenever wealthy nations – those with powerful armies and gold – strived only for empire and easy fortunes to support welfare at home, those nations failed.