After completing the first version of this comment (September 2003), we became aware of a paper (Rustichini and Siconolfi 2003) in which a point similar to ours is made. We wish to thank the editor, Robert Shimer, and two anonymous referees for very helpful comments. Financial support from the Ministry for University and Research (project 2005135328_002) and the School for Advanced Studies in Venice to Gottardi and Fundación Ramón Areces and Spanish Dirección General de Ciencia y Tecnología (projects SEJ2004-07861 and HI2001-0039 and Ramón y Cajal Program) to Jerez is gratefully acknowledged.