I love the spirit of this piece. I have seen it manifest at times in my life. However, I still tend to agree with David Allen’s philosophy on calendars: the only things that should go on your calendar are things that will die if they don’t happen on that day, at that time.
The reason I still tend to agree with David is this: once you have a bunch of stuff on your calendar — which you know are not things that will die if not done then and there — the odds increase that you will simply go numb things on your calendar. Once that happens, you are breaking commitments to yourself. Doing that undermines productivity.