Ian Yorston found an interesting article by Charles Leadbeater, How to Profit from Ignorance:
In the knowledge economy, we all become richer by becoming relatively more ignorant. We trade our know-how with one another but reveal our ignorance in the process. Ignorance is not quite bliss, perhaps, but it can be far more productive, creative, and efficient than people give it credit for. In the knowledge economy, we all become richer by becoming relatively more ignorant. We trade our know-how with one another but reveal our ignorance in the process. Ignorance is not quite bliss, perhaps, but it can be far more productive, creative, and efficient than people give it credit for.
While knowledge is important, it is also useful to know where my expertise ends, so I don't bother myself with trying to figure out things that others already know. This is important for me, since I like to think of myself as a know-it-all. Knowingly not knowing-it-all may actually be more helpful. See the Levels of Ignorance in the comments of this post.
And then there is always humorist Jim Boren's approach to ignorance, "The purpose of ignorance is to liberate the minds of people from the restraining chains of knowledge."