Two regional US banks said they were the victims of fraud on loans to funds that invest in distressed commercial mortgages. Zions Bancorp sank 12% after it disclosed a $50 million charge-off for a loan underwritten by its wholly-owned subsidiary, California Bank & Trust. While Western Alliance Bancorp tumbled almost 11% after it said it made loans to the same borrowers. Bloomberg's Sally Bakewell joined Carol Massar and David Gura on 'Bloomberg Businessweek Daily' to break it down. ...