I loath sending the "You didn't get your 'A'" emails. I actually don't mind the "You failed" emails or the "You plagiarized so I'm hoping to get you kicked out of the university emails" nearly as much. It's so hard to explain to students - the ones I respect and know that worked hard - that they did really well, but slipped up on a minor but testable item. I know that so many students at my school just don't get A-s. Their parents are going to freak out. They think their chances for grad/med/law school are completely shot. I hate being the guy that gets to explain it to them.
It would be so much easier if I really didn't like them.