RE: Spine shots
I have never AIMED for the spine, but several of the deer I've killed over the years were spined. It's a horrible thing to witness as the deer struggles with it's front legs only attempting to get away from you as you grab another arrow to finish the job.
I was fortunate and have always been able to quickly dispatch the deer with follow-up shots, but the scene that played out each time haunted me for days (and months) afterwards. It may happen again to me someday, but it won't be intentional.