Simple. Download the Steve Jobs' MacWorld keynote address which you can download here or from iTunes.
OK, so Steve has his reality distortion field and a very partisan audience on his side to laugh at his jokes, clap without a cue card, etc. etc.
But he also has what it takes to pull off a presentation that lasts about and hour and a half. And if to prove the point, I bet there is only only part you will want to fast forward through and that is when Cingular's CEO is invited on stage, complete with his pack of cue cards.
Of course, it could be that Steve purposely chooses such guests to set him in an even better light.