Microsoft's unsolicited US$44.6 billion bid to take over Yahoo has helped push Bill Gates off his perch atop Forbes' rich-list, ending his unbroken 13-year run as the world's richest human.

According to Forbes, Microsoft shares fell 15 percent between 31 January -- the day before it announced its bid for Yahoo -- and 11 February, when Forbes took its snapshot of share prices for the 2008 World's Billionaires list.

Forbes believes the outgoing Microsoft chairman is now worth US$58 billion -- up US$2 billion from a year ago and enough to take bronze in the global fat-cat stakes. Top of the list is Warren Buffett, Gates' sometimes bridge partner and chairman of holdings company Berkshire Hathaway, who has a fortune estimated at US$62 billion, up US$10 billion from a year ago.

Number two in the world is Mexican telecoms billionaire Carlos Silm Helu, worth an estimated US$60 billion. The rest of the top 10 includes metal moguls, an Indian real-estate giant and the founder of Ikea, Ingvar Kamprad.

Oracle chief Larry Ellison made it to number 14 on the list, with US$25 billion to his name. Ellison has dropped three places since last year, despite being $3.5 billion richer.

Setting out his own stall on billionaire's row is Mark Zuckerberg, chief executive of social-networking site Facebook.

Zuckerberg earned the accolade of being the world's youngest billionaire, with his relatively modest US$1.5 billion at 23 years of age. Forbes speculated that Zuckerberg "might just be the youngest self-made billionaire in history", adding that 2008 is "a record-breaking year for young billionaires".