Sadly, I've heard about this before, and several years ago I read an article about how people are led into believing that animals traveling in the cargo area are pefectly safe.
It seems that in reality the airlines cannot guarantee proper temperature and atmospheric conditions in the holds. I've never had to travel with an animal by air, but should I ever need to take my cat with me on a plane in the future, he will ride with me in the passenger section or we will not go.