Warren Buffet is not taking a huge risk. All though he sounds like a hero rushing to the rescue and making a gamble the reality is far from that. With his $5 billion he has negotiated a position where his stock will be a grade above the preferred. He will get 10% per year gauranteed and option to double down in 5 years for the same amount of shares at the same price as purchased last week.
His $5 bil will be the first money repaid in case of a bankruptcy and if any is left it will go to the preferred share holders. Pretty shrewd dude. The best value play here is Berkshire Hathaway.