After some of the most turbulent trading days experienced by Wall Street in a generation, the latest list of America's top 400 richest people produced by the business magazine Forbes looks like a window into a bygone world.

The Microsoft chairman, Bill Gates, still tops the list with a net worth of $57bn (£31.7bn). But how safe is the second-place position of the famous investor Warren Buffett - his $50bn fortune has dropped $12bn in six months - since the list was compiled at close of play on August 29?

Since then the Dow Jones has dropped more than 800 points in just four days, Lehman Brothers became the world's largest ever bankrupt, Merrill Lynch was forced into a shotgun wedding with Bank of America, AIG was bailed out by the US government and Morgan Stanley is on the brink of collapse.

AIG's woes earlier in the year had already pushed one of the insurance group's major shareholders, Eli Broad, down to No 48 on the list with an estimated wealth of $6.7bn. A well-known philanthropist, he sold his SunAmerica business to AIG and the proceeds have helped not only his adoptive city of Los Angeles but the nation's art dealers. He owns the world's largest collection of works by Jeff Koons and once bought a painting by Roy Lichtenstein for $2.5m using a credit card. The government bailout of AIG, however, will have significantly hit his wallet since the Forbes 400 list was compiled.

It is unlikely that art will retain its value in the current slump, despite the record-breaking Damien Hirst sale earlier this week. This will come as a shock to Donald and Doris Fisher, the founders of the Gap clothing chain who returned to the list in joint 377th place - on $1.3bn - thanks to their $1bn art collection which includes pieces by Chuck Close, Richard Serra and Alexander Calder.

The couple share their spot with the former Citigroup boss Sandy Weill, who can also expect the recent turmoil to have hit the value of the shares in the bank he still owns - he had already lost $500m over the year to the end of August. The position of fellow Citigroup shareholder Gerald Ford - who sold Golden State Bankcorp in 2002 for $6bn to the bank, and is listed at No 355 with $1.4bn - also looks rocky.

Back among the big hitters, Wall Street's crash and the demise of Lehman Brothers will have hit the $15bn fortune of 15th-placed Abigail Johnson. Her family runs Fidelity Investments, which is understood to have funds with some of the highest exposure to both the collapsed investment bank and AIG. Her father Edward is placed at No 28 with $11bn and is level-pegging with George Soros.

Soros ranks highest among those in the Fortune 400 whose wealth comes from hedge funds and private equity and it is unlikely that all the other 23 in the list who have made their money the same way will be there in a year's time.

The Bridgewater Associates boss, Ray Dalio, is ranked at No 78 with a fortune estimated at $4.5bn, while the Och-Ziff hedge fund co-founder Daniel Och is at No 95 on $3.9bn. Also at No 78 is John Paulson, who has made millions for his funds over the past year by betting against sub-prime assets. The firm's Credit Opportunities fund was up 590% net of fees last year.

As well as wiping out billions in paper fortunes as share prices collapse, and perhaps raising billions more for shrewd investors, the impact of the turmoil in the banking sector is likely to hit other industries.

Particularly vulnerable is Michael Bloomberg, who sits in eighth position with a $20bn fortune. The collapses and mergers in the financial industry are likely to significantly reduce demand for the news and trading terminals that bear his name.

Elsewhere, Google's Sergey Brin and Larry Page come in at 13 and 14 with $15.9bn and $15.8bn respectively. Lawrence 'Larry' Ellison, the boss of the software company Oracle, comes in third at $27bn, while spaces four, five and six are taken up with the Wal-Mart dynasty who together control more than 39% of the grocery chain, which owns Asda in the UK. Jim Walton, the son of the supermarket giant's pioneer Sam Walton, comes in fourth at $23.4bn; his elder brother and the company's chairman, Robson Walton is in fifth on $23.3bn, and their sister Alice is joint sixth with $23.2bn with the widow of her other brother John, Christy Walton, and her family.

Finally, the Facebook founder Mark Zuckerberg can afford a wry smile. He is the youngest member of the Forbes 400 thanks to the $15bn valuation placed on the social networking site when Microsoft took its 1.6% stake last year. His $1.5bn fortune puts him at number 321. At the time he was being pushed to float the business, which he set up four years ago. If he had, it would now be buffeted by the current market turmoil and it is unlikely he would have the minimum $1.3bn fortune needed for inclusion.