In front of a ballroom full of N.C. bankers in January 2006, Wachovia chief executive Ken Thompson warned of the dangers of “toxic” home loans. A problem with so-called option adjustable-rate mortgages, he told the group, was that homeowners can end up owing more at the end of the month than the beginning, which can be a “tough situation” for customers and lenders. “I have literally been amazed at the terms offered by some mortgage lenders, thankfully not at Wachovia and thankfully not so much in North Carolina,” he said. Four months later in May 2006, Thompson took a $24...