My goal (and I hope I achieved it) was to be technically accurate but explain Bitcoin to people who have heard the term but have no idea what it is or how it works.
I'd like to suggest that in the future when you face a similar goal you start with the why first and then go on to what and how following the advice presented in this video?:
http://www.youtube.com/watch?v=qp0HIF3SfI4I think it's a much more powerful introduction if your audience can first emotionally connect to what you are introducing.