The top 10 richest people in the world have a combined worth of 342 billion dollars in 2010, up from 254 billion a year ago.

Here are the 20 wealthiest, as announced Wednesday by Forbes magazine in its annual list of the world’s billionaires:

1. Carlos Slim Helu and family. Mexico. Telecoms. 53.5 billion dollars.

2. Bill Gates. US. Microsoft. 53 billion dollars.

3. Warren Buffett. US. Berkshire Hathaway. 47 billion dollars.

Castles in France. Islands in the Caribbean. 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 billionaires 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 of 140 countries, including Costa Rica, El Salvador, Bolivia and Uruguay.

The American national business magazine, Forbes, compiled and published the list of billionaires including the world’s wealthiest people as of the first quarter 2009, based on each person’s total net worth.

Bad news for rich people: last year there were 1,125 billionaires, but this year there are just 793 people rich enough to make the list that means a 30% decline from a year ago.

The world’s richest are also a lot poorer. Their collective net worth is $2.4 trillion, down $2 trillion from a year ago. Their average net worth fell 23% to $3 billion.

“Billionaire Bust”, is the red title on the cover of this month’s Forbes special issue that demonstrated how hard the crisis had struck on the richest people on the planet.

The saga of world’s most expensive house started over at luxuo with Updown Court, the most expensive mansion in the world and the100 Million Dollars Trump’s Palm Beach Mansion.

As a matter of fact, one of our reader, who left a comment, was right : some villas on the French Riviera might be even more expensive !

Various sources said Russian billionaire Roman Abramovich and his girlfriend Daria Zhukova have just bought a home in France for $500 million. The home in question, La Leopolda, is an elaborate villa located on the French Riviera… which has become the world’s most expensive house !

Bill Gates is now only the third richest man with a net worth of $58 billion. Mexican telecom mogul, Carlos Slim Helú, trumps Gates by $2 billion.

Had Microsoft not made an unsolicited bid for Yahoo!, Gates would have kept the number one spot, which is now filled by Warren Buffet.

Naturally, the list had no shortage of Andrei’s, Sergei’s or Dimitri’s. However, it only places three Russian billionaires in the top 20.

Oleg Deripaska, Roman Abramovich, and Alexei Mordashov all share the title of “self-made” and each have made their fortune in aluminum.