[PeterisP]

If you do lose one day, and everything is full, then you do have to adjust stuff anyway, and it forces you to do that.

You don't put things on calendar that you might do - you put things that you will or must do then; and it is important that if something (like that sickness) means that you won't be able to do all X things, then you can know early and choose appropriately which one you won't do in the expected time.

Also, in your Techcrunch example - it makes you informed about the consequences; if you get an option to do a large thing then you'll see what other important things you will be displacing and is it really worth it compared to those other tasks.