I believe I was too quick to post this topic. My co-worker Sieg Lindstrom points out that an athlete need only compete at the USATF meet, not in each particular event, to be granted the Worlds defending champ spot. Marion only ran the 200 in '01 but ran the 100 in Edmonton. Mo ran one round in Eugene '01 because he didn't compete in the 200.
In any case, he should be on the team just because damn near every track fan in the world wants to see Tim Montgomery and Maurice Greene face off in the 100. It would even get the attention of casual track fans. That's good for the sport.
Okay, maybe every track fan except Tim Montgomery's mom.