I see your point, but when I hear "exceptions to every rule" I want to explore the boundaries of those exceptions. I think that presentations are creative performances, essentially, so it's likely that the number of exceptions are going to be large.
It's just like every other artform - the rules are there to give people a framework they can work from, but the best performers break the rules. Clifford Stoll is a great example of this.
You can see Jessica Livingston pacing back and forth here: http://blog.businessofsoftware.org/2008/12/jessica-livingsto... It is annoying, and she seems nervous.
Note: This is not meant to pick on JL, very few people get it right, and I could just as easily have picked another example.