[mbh]

I am sorry but OP is missing the point here. A good speaker knows his audience and hence prepares his talk accordingly. If it is techies, he should put for technical content which stimulates their brain. If it is children of the 3rd grade, he should know to keep it light and crack jokes or tell stories. A good speaker will change his speech depending on how dumb or intelligent the audience is. Thats his trait. Now if he has a large and varied audience, this task gets a lot harder, but then again there is a trend in the audience.