I liked your 5-min summary. Pretty good job, I'd say.
A couple of nitpicks: you mentioned that the reasons why AI can be bad are "technical" and "complicated", while showing a near-empty slide. I don't think that makes a convincing impression. Later on, you mentioned the "utility function", which extends the inferential distance a bit too far. Your last example, tiling the universe with smiling faces, seemed to fall flat, probably a sentence or two would fill the gap. In general, the audience's reaction shows quite clearly what worked and what did not.
PS: thanks for your advice, btw
I did a talk at the 25th Oxford Geek night, in which I had five minutes to present the dangers of AI. The talk is now online. Though it doesn't contain anything people at Less Wrong would find new, I feel it does a reasonable job at pitching some of the arguments in a very brief format.