I agree that it's unfortunate so many people abused the doctor's note; the same abuse is the reason some airlines want to see an actual death certificate for a bereavement fare.

As for insurance: I only buy it if there are other nonrefundable expenses (tour package, cruise, etc.), because the premium is usually more than the $75 airline change fee! Yes, I realize the insurance covers other things (evacuation, etc.) but those aren't worth much to me - if I'm well enough to start a trip, I'm probably going to be well enough to finish it (I hope). Besides, at 20 to 30 trips per year, it would get pretty expensive!