CNNMoney’s well-respected senior editor-at-large, Allan Sloan, has a warning for municipal bond investors ? look out below, because even investment grade municipal bonds are mega-inflated by lighter-than-air interest rates and are sure to pop when interest rates (and tax rates) rise. Repeat: high grade munis, he says, are at risk (“Municipal bonds: A train wreck waiting to happen,” Allan Sloan, CNNMoney).