Unlike most of the other posters, I don't feel any need to defend procrastination. Like Ferrari says, it is mostly bad. But it's surprising that Ferrari does not have a better explanation, since there is nothing surprising about procrastination from an evolutionary perspective.

During most of humanitys existence, we have been preoccupied with work that was A) non-intellectual, which means it's easy to pick up and B) strongly enforced by the group. Staying in bed while your family went working in the fields was not an option. Instead, being able to daydream while you were working was probably advantageous, since it meant you could put up with it better. Intellectual work was done by people in the upper classes who only did things they personally enjoyed, like Da Vinci.

What we have now is a historically unique situation: a large part of the population do work that is both intellectual and boring, without anyone prodding us to do it. No wonder it doesn't work out for a lot of people.