If you don't work on important problems, it's not likely that you'll do important work.
Perhaps the central problem we face in all of computer science is how we are to get to the situation where we build on top of the work of others rather than redoing so much of it in a trivially different way.
He who works with the door open gets all kinds of interruptions, but he also occasionally gets clues as to what the world is and what might be important.
