Buffett: Greece shows weakness of 'shared currency' concept

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Berkshire Hathaway increased its net worth by $18.3 billion last year, the company said in its 50th annual letter on Saturday, with a "good year" marred in part by underperformance at its Santa Fe railroad unit.

The Omaha, Nebraska based conglomerate run by billionaire Warren Buffett also dropped a big hint that the era of its larger-than-life CEO was nearing a close.