Muni Blues Worry InvestorsGrowing Fear That Cities Will Default—Not Out of Necessity but as a StrategyArticleComments 56MORE IN BUSINESS »smallerLargerBy MICHAEL CORKERYSome cash-strapped U.S. cities are walking away from their financial obligations, exposing potential risks in the municipal-bond market.The moves are reminiscent of the strategic defaults seen during the financial crisis when many homeowners, overwhelmed by spiraling debts, mailed house keys to lenders and stopped paying their mortgages—a trend known as “jingle mail.” Now some cities are confronting similar dilemmas, and their choices could have repercussions on workers, taxpayers and bondholders.