Buffet wouldn't use leverage when shorting put contracts. He probably has those $4.7 earmarked and set aside in cash equivalents collecting interest until they all expire. Either he goes long when they end up in the money or he doesn't.Quote from nailer225:The options expire between 2009 and 2013, and could expose Berkshire to losses as large as $4.7 billion.
Hard to "blow up" when you don't use leverage.