Ignore the previous post, procrastination is a great thing and the world needs it.
If I spend hours and hours on end 'working', I get the job done, but, depending on the task, I can be more productive with a decent amount of procrastination. After staring at the same screen for hours you can lose track of what you're doing. With just a little bit of procrastination to loosen your mind you may find yourself solving the problem in five minutes instead of five hours. Keeping the mind creative and free is extremely important, and procrastination helps.
A recent practical example comes to mind. I was thinking about how to design a website for a mobile phone. In-between learning about html, xhtml and whatnot I got bored and checked Hacker News, which happened to feature JQuery Mobile, a framework for building mobile websites. It was exactly what I needed, popping up in front of me at exactly the right time, but there are other examples of less convenient timings as well. I learned about Django, Hibernate, SQLite, Android mostly by procrastinating, reading articles about those topics while working on projects that had nothing to do with them. The knowledge lingers in my brain and helps me make decisions at a later stage, for example when deciding which server-side framework to use, or how to store data on a mobile device. If I had just kept my head down and kept programming I would not have learned a lot of topics.
Mostly though, I really want to emphasize that among all the people I know, the people who procrastinate the most are also the most interesting to talk to. On the scale of salaryman versus freedom loving hippies, procrastinators are tending towards the fun side. And that might be more important in life than just being productive.
(but it might not be...)