This had me scrambling to make sure that my definition of 'Thought Leader' was correct. [I'd hate to be the guy from Princess Bride yelling "Inconceivable!"] So, I quickly went to Wikipedia and got the definition:
Thought Leader - A person who is recognized among peers and mentors for innovative ideas and demonstrates the confidence to promote or share those ideas as actionable distilled insights.
My definition was a little simpler: "A person who comes up with some good ideas, and like spaghetti, throws them against a wall to see what sticks."
In my retweet I was thinking that the blog could equal the wall, and the sticking would be the ability for the thought leader's ideas to stand up to the comments of his or her readership. In a way, you could think of it as a "quasi peer-review" process. A great example of this would be my co-blogger Toby Brown's post on GMail and Privilege. Toby threw his ideas of what happens when you combine legal ethics rules against a Terms of Service agreement from an email service provider. He tossed out his interpretation on the blog (for God and everyone to see), and found that his peers both agreed and challenged him on his interpretation.
Jeff is correct in that Thought Leaders do tend to 'comment' more than they teach on their blog, but in a way they are challenging their readership to either accept their comments as a great innovative idea, or to point out the flaws in their ideas. In the "old days" we would have to meet them face-to-face or write them letters or emails to engage in the discussion. Those conversations, however, would be limited to the audience in attendance or would simply be a one-on-one conversation. With blogs, those leaders can be engaged in multi-party conversations over a period of time.
Now, I might be stretching the definition of "Thought Leader" slightly (or in Toby's case... enormously!), but I do think that blogs are an excellent platform for though leaders to discuss their ideas and generate feedback from their peers. If you fall under my loose definition of "thought leader", I expect to see some spaghetti sticking on the walls of your blog.