TMI

Someone in the photography class I'm taking just sent an email to the whole group going into great detail (dates, times, test results, ward number etc) about the medical emergency that kept her and her husband from attending the last class. I felt kind of uncomfortable reading it (I really don't need to know your family and medical histories). I mentioned this to a housemate and he pointed out that my mum would probably appreciate an email like that. In fact, my mum would likely send an email like that.
My little brother's girlfriend was in a car accident just before they were flying to see her family last week. She was okay, but her back was still hurting a bit when she got on the plane. My mum wanted my brother to tell the flight attendants about the accident, because she thought they should know, "just in case", but my brother disagreed. My mum told me this story as an illustration of how my brother can't bear to think/talk about bad things and just ignores them entirely, but I'm totally on his side. Seriously, why would it help to inform anyone? Are the attendants going to do anything other than say "I'm sorry, let me know if you need anything", at most? Why not just wait and say something if you do actually need anything?
My housemate also said that he knows far more about my mother's life, from the few minutes of talking to her when answering her calls, than he does about mine. I know I'm ridiculously secretive and obviously there is a middle ground, but I'm not sure I can recognise it. It seems much safer to say nothing than risk overloading people with information they don't want to hear.