Bill Gate's mother first brought the two men together in 1991. The Microsoft founder didn't have the slightest interest in spending a day with one of those guys who spends all his time thinking about stock shares. "What were he and I supposed to talk about, P/E (price to earnings ratios)?" he would later write.

It turns out they had a lot to talk about and more than a decade on, Bill Gates and Warren Buffett have become good friends. The software genius and the investment guru even play bridge tournaments together in Omaha, the two card players at the table looking like a friendly pensioner and a middle-aged high school teacher.

Fifteen years after that first meeting, the unusual friendship has led to one of the most incredible and valuable gifts ever seen in modern history. With his $32 billion donation to the Bill and Melinda Gates Foundation, and further billions for his family's charitable projects -- Buffett has transformed himself, overnight, from being the ultimate capitalist to become the man who is likely the biggest charitable donor in the world.

Already in his 20s when he was making his first small investments he had planned to give some of his future wealth back to society, Buffett has said. Back then, his wife didn't think much of his big talk. "She either didn't care or didn't believe me," he recently told Fortune magazine.

There are many alternative scenarios for what Buffett could have done with his money. He could have founded a Buffett University in his hometown of Omaha, Nebraska which would have been even better equipped than Harvard. He also could have set up his own foundation in order to compete with Gates for the title of greatest philanthropist. After all, oil tycoon John D. Rockefeller deliberately set up his Rockefeller Foundation with a $450 million dollar endowment -- $100 million more than that of steel baron Andrew Carnegie, who up until that point had been considered the most generous of America's tycoons. "A man who dies rich, dies in shame," Carnegie once famously stated.

Buffett also could have just left his money to his children. Fortunately for the world's less fortunate, Buffett would rather give them a helping hand than a free trust-fund ride to his children. Indeed, he finds unbearable the old money idea that future generations of his family should be able to coast off the fortune he amassed, "just because they are the members of a lucky sperm club."

The Gates Foundation today spends $800 million a year in the fight against AIDS, malaria and tuberculosis -- the equivalent of the World Health Organization's annual budget or the amount the United States government spends on containing infectious diseases. Buffet's donation doubles the foundation's funds which have been gathered since the mid 1990s and now makes Gates one of the most important actors in the Third World -- one who doesn’t have to justify his decisions to anyone. "We are in this unusual position where we can spend $100 million dollars on something we think might work and it can fail and nobody gets fired," the Microsoft founder has said.

A bright future for philanthropy

He expects Buffett's donation of billions to inspire other members of America's super rich to give. "I hope we're seeing a rise in philanthropy and that people with wealth will give wealth back," he said. The chances of this happening among America's rapidly growing billionaire class don’t look too bad, either. The founders of Dell, eBay and Google have already established considerable foundations. "Giving is now what you are expected to do," said Vartan Gregorian, the head of the Carnegie Foundation.

At the same time, state development aid is being criticized as too bureaucratic and not effective enough. But in the end can entrepreneurs achieve more and provide more effective aid with business, results-orientated methods?

There have also been a number of objections to the philanthropists. Aid workers complain, for example, that the Gates Foundation has invested too much money in research into vaccines and not enough into important life-saving measures such as mosquito nets. Gates considers this dispute to be a "healthy dialogue" and has begun to vary his projects. Eighteen months ago, for example, Gates began a microcredit program that enables Africans to take small loans to help the establish a livelihood. A loan of $50 would be enough to set a person up with a loom or other tools crucial to a vocation.

The odd couple

In the world of philanthropy, these guys could give Felix Unger and Oscar Madison a run for their money. The fact that the two are self-made billionaires seems to be the only thing they have in common -- at least on the surface. The one, Buffet, who still lives in the same, relatively modest gray-stucco house in Omaha that he bought for around $30,000 in 1957 at the age of 27. And the other, Gates, who built a 3,700 square kilometer complex of buildings in Seattle, which is valued at $125 million -- a futuristic rambling villa, in which there are 82 kilometers of cables, and the bathtub is automatically filled when the man of the house is on his way home.