I've been thinking about this a bit after the shootings in Norway, and the deadly earthquake in my city a few months ago. I think that I have two requirements in order to be able to die happily: that I have said everything I need to say, and that other people can understand me (think 'speaker for the dead', so that people can understand what was important to me and what I believed in). I have many things I want to do before I die, but if these two needs are provided for, I can honestly die without regret. Everything else is just dependent on me living out my convictions.
Certainly we should regularly tell people that we love them, that they are important to us, etc, but I think being able to say a final goodbye is an entirely different thing. I hope my brother understands how much of a role model he is to me (and I will try to make sure he does know), but even so I would appreciate the chance to say so, one last time. My parents know I love them, but I think they would treasure a post-mortem letter saying exactly that.
However, I agree with everyone who pointed out that emails are a bit impersonal. I would prefer to be able to hand-write letters, and have them automatically posted via regular mail. I think that would be a pleasant surprise.