To add to the chorus: Douglas Adams. Not only was the Hitchhiker's series incomplete, his nonfiction stuff on technology was hilarious. If you've read Salmon of Doubt, you know what I'm talking about. He could have had a long second career blogging, we can now only imagine his fascination with what the internet has become.
Also, he's the only person who could potentially have got me to sign up for a twitter account, just to follow his assuredly awesome tweets. Search your feelings, you know it to be true.
RIP you hoopy frood.