Very nice article, I can definitely see these behaviors in myself and in others.
One other factor that can hinder the spread of knowledge is the "It's easier to do it myself" trap. When a problem or high-priority task in your area of expertise comes up, it's often easier to just take of it yourself than it is to share your knowledge and show someone else how they can handle it. With the best of intentions ("I'm going to take care of this right now") you can miss the opportunity to spread expertise around. I find myself in this situation often, and I've got to admit that I speak from experience when I say that it is easier and faster to just do it yourself. But I also know that it benefits the organization when I take the opportunity to educate others in my area of expertise. And it helps me, too -- while it can be enjoyable to be the "go-to" guy, it can also be exhausting. So your article is a good reminder. Thanks!!