http://online.wsj.com/article/SB120061980722699349.html?mod=googlenews_wsj With no central trade processing of credit-default swaps, defining trading-partner risks can be a Herculean task. Mr. Buffett learned the difficulty of unraveling such complex instruments in 2002 when he directed General Re Corp., a reinsurer that had been acquired by his Berkshire Hathaway Inc., to pull back from the business of these swaps and other derivatives. It took General Re four years to whittle the business from 23,218 contracts to 197 by the end of 2006. Doing so involved tracking down hundreds of counterparties to General Re's trades, many of which Mr. Buffett and his colleagues had never heard of, he says, including a bank in Finland and a small loan company in Japan, to name just two. One contract, Mr. Buffett says, was designed to run for 100 years. "We lost over $400 million on contracts that were supposedly" safe and properly priced, "and we did it in a leisurely way in a benign market," Mr. Buffett says. "If we had to unwind it in one month, who knows what would have happened?"