The most knowledgable, experienced and insightful folks are often the most up-front about what they don't know

Bay Journal editor Karl Blankenship (who just joined the blogosphere) is one example :

Possibly the most untrue things said about the Bay are any of the variants of the phase, "We don't need any more research. We know what needs to be done to restore the Bay, we just have to do it."

I sometimes tell people that I spent the first 10 years with the Bay Journal learning about the Chesapeake. I spent the next 10 years learning how little I know about the Chesapeake.

The Bay is a magnificently complex system, and every time I start to get cocky and think I understand it, something comes along to humble my pretensions toward higher intelligence.

Gary Jones, the long-time grass farmer and veteran blogger, also comes to mind:

I've often said that everything that I know is wrong, I just don't know how it is wrong or what is right. It's why fallibilist philosophies and heuristically diverse problem solving groups appeal to me, and why experts, intellectuals and other sorts of immodest posers seem so ludicrous. Their self-esteem is proof of ignorance and stupidity.

UPDATE: Somewhat related: Gary on the difference between intelligence and glibness.