Yesterday was opening day at the famed and celebrated Del Mar Racetrack – “Where the Turf Meets the Surf.” Great food, summery libations, wacky hats, hobnobbing, glass-tipping, shoulder-rubbing…and death? In the 6th race yesterday afternoon (yes, they put on horse races too), a 3-year-old filly named Presidential Air “broke down” – to be more specific, snapped a leg – and was euthanized. Dead. Which leaves me wondering: How many of those 42,000-odd revelers were/are aware that part of the day’s entertainment was killed? More important, how many care?