"...the best 3-year-olds in this country in the last three years have all been dramatically - and prematurely - removed from racing through injury. Last year it was Afleet Alex, before that Smarty Jones and now Barbaro. What's going on?"
Let's look at this statement again. Only Barbaro was hurt in a "dramatic" fashion. The other two were hurt in training. Relatively minor injuries at that. They are worth so much, it is not worth the risk to put the horse on the farm for 6-9 months just to race again when a Derby winner is worth 50/60 million at stud.
Remember- Secretariat stopped racing after his three year old season. Did he stop racing "prematurely?
Seattle Slew, Affirmed, Spectacular Bid after 4. Cigar did not even get good until 5. We have no idea how good some of these horses could have been.
True enough... can't argue with that :~D