A question that comes up very often in my Great Presentations class is — “What do you think about memorizing a talk?”
The question of memorization touches on the three central parts of a talk: the preparation, the practice, and the delivery. These three areas constitute the most profound parts of a formal talk, so your decision about whether you will memorize requires thoughtful consideration.
My deeply-held view is that memorization is 100% fine — as long as the delivery is natural, and as long as the story is perceived by the audience in a comfortable way.
I have seen the entire range of possible outcomes from speakers who present a memorized talk. I have listened to painful, uneven, disconnected discourse with unnatural intonation, speed, and pacing, along with the stiff posture that often accompanies a poorly-delivered memorized talk.
And I have also watched memorized talks that were so well-rehearsed you would never know that the material was memorized word for word; gesture for gesture. In fact just such a wonderful talk was presented in my presentations course at Columbia University last week by Computer Science student Angela Fox.
Play with memorization if this is your preference. Ask for feedback so you have a clear idea of audience perception. And always remember your goal — the delivery of an interesting, understandable, and exciting presentation story. If you can achieve your goal through nuanced memorization of your script, then go for it!