From the WallStreetJournal.com:
 
Just days after becoming Controller of  financially strapped Harrisburg, Pa., in January, Daniel Miller began  uttering an obscure term that baffled most people who had never heard  it and chilled those who had: Chapter 9.
The seldom-used part of U.S. bankruptcy  law gives municipalities protection from creditors while developing  a plan to pay off debts. Created in the wake of the Great Depression,  Chapter 9 is widely considered a last resort and filings under it are  more taboo than other parts of bankruptcy code because of the resulting  uncertainty for everyone from municipal employees to bondholders.
 
The economic slump, however, is forcing  debt-laden cities, towns and smaller taxing districts throughout the  U.S. to consider using Chapter 9. As their revenue declines faster than  expenses, some public entities are scrambling to keep making payments  on municipal bonds. And that is causing experts to worry about the safety  of securities that are traditionally considered low risk.
 
"People believe that municipal debt  is safe based on assumptions that are no longer true," says Kenneth  Buckfire, managing director and chief executive of Miller Buckfire &  Co., an investment bank that has worked with corporations on restructurings  and now is advising municipalities. For example, it isn't safe to assume  that governments can raise taxes to cover shortfalls, he says.