It seems that there are two categories: those schools that are lax, and those schools that want proof that you're going to be doing something "life altering" during your time off.
JBJ's post is correct, you'll need to check with each school. However, you may want to do this research anonymously. Some schools won't look favorable upon an applicant who is planning to defer. By the way, are you applying for 2003 or 2004? It's really late for a 2003 deferral, IMO.