A key issue to consider when purchasing bonds is the risk as to whether or not the company will be able to stay out of bankruptcy, or will default on the debt. The U.S. government has virtually no risk of defaulting on a bond; as the issuer of currency, it can just print more money to cover any bond it issues (with associated inflation). Municipal bonds HAVE defaulted in the past, but those individual incidents are historically significant: it happens exceedingly rarely.