These American moguls could buy some of the world's economies

Castles in France. Islands in the Caribbean. Private jets. With a collective $1.27 trillion at their disposal, the members of The Forbes 400 could buy almost anything.

How about a country? A quick glance at the CIA Fact Book suggests the individual fortunes of many Forbes 400 members are as big as some of the world's economies.

Bill Gates, America's richest man with a net worth of $50 billion, has a personal balance sheet larger than the gross domestic product (GDP) of 140 countries, including Costa Rica, El Salvador, Bolivia and Uruguay. The Microsoft (MSFT) visionary's nest egg is just short of the GDP of Tanzania and Burma.

Warren Buffett, who lost $10 billion in the past 12 months and is this year's Forbes 400 biggest dollar loser, still has a fortune the size of North Korea's economy at $40 billion. (The Oracle of Omaha probably would steer clear of that investment, though.)

One Forbes 400 member does actually run a small chunk of a state in an official capacity: Mayor Michael Bloomberg. While he is busy serving as the chief executive of New York City and grappling with its sluggish economy, his own personal balance sheet -- amassed through financial information services and media company Bloomberg LP -- equals the value of all the goods and services produced in South Africa's Republic of Zambia's ($17.5 billion).

Some say that land developer Donald Bren, whose assets throughout the vicinity of Orange County, Calif., include 475 office buildings, 115 apartment communities, 41 retail centers, resort properties and new housing, runs Orange County -- he certainly owns most of it. And with a net worth of $12 billion, he could, in theory, buy Haiti's economy, too.

Casino mogul Sheldon Adelson's $9 billion net worth is akin to the Bahamas' GDP ($9 billion). Pierre Omidyar, founder of eBay (EBAY), the world's biggest auction marketplace, could theoretically control Somalia's market with his $5.5 billion fortune.

George Lucas, the famed Hollywood director behind the Star Wars and Indiana Jones franchises and ILM, the world's most bankable special effects shop, has a $3 billion fortune, making him worth as much as the GDP of Guyana.

Hedge fund founder David Shaw's $2.5 billion net worth parallels Belize's marketplace.

Investor John Paulson amassed much of his fortune by exploiting the real estate bubble and shorting the subprime market in 2007. Today he has a net worth of $6.8 billion -- the equivalent of Montenegro's gross domestic product.

Although Eli Broad's fortune suffered because of AIG's (AIG) collapse last fall -- he's lost $1.3 billion in the last 12 months -- he still has a bank account that rivals Barbados' economy ($5.4 billion).

Forbes 400 members with net worths just under $1 billion still possess fortunes that could operate the economies of significant fractions of the globe. Gary Magness, who owns water rights in Colorado through his ranch holdings, has a net worth of $990 million, which barely exceeds Vanuatu's GDP ($988.5 million).

If this year's three poorest Forbes 400 members were to combine their wealth (a combined $2.9 billion), their amassed fortune would be worth more than the workings of Belize's entire economy.