So it goes for bears on Toshiba Corp., who’ve spent the last seven months covering short sales on the electronics maker after pushing them to a decade high in May. Bets against the stock hit the lowest level of the year this week, just in time for it to plummet more than 40 percent in three days on word of a writedown at its U.S. nuclear services unit. Now credit swaps are surging as rating agencies downgrade their outlook on the company.