Each year the faithful make a pilgrimage to Omaha, Nebraska. Some 15,000 people descend on this unremarkable mid-western town, anxious to hear the wisdom of their humble guru. It is an event surrounded by ritual, adulation and a fair degree of cult worship. But this is not a religious sect, it is a shareholders' meeting. It's a billionaires' convention - probably the largest gathering of private wealth at any one time, anywhere in the world. Their guru, Warren Buffett, is an unassuming man in his late sixties. He also happens to be worth over $30 billion, making him the second richest man in the world.