Many of my hours each week revolve around speaking to prospects and giving presentations for my company. Often during these presentations and conversations I get into SEO/SEM topics and explain the fundamentals of SEO (a little presentation). I have given one real seminar that took place over a 3 day span on several topics including SEM, the SEM topic filled up about one full day.
Why do I bring this up? Well, there is a thread over at HighRanking's named Making Speeches and many SEM/SEO professionals who speak publicly discuss the challenges and rewards involved in public speaking. Check out the thread here.