We've all heard the phrase "death by powerpoint" and we've all sat through interminably dull presentations, talks and lectures. However, I came across an article yesterday called "No excuse for boring an audience: Advice on giving technical presentations," which makes the fairly obvious point that usually it's not Powerpoint's fault but the presenters. Borring presenters give borring talks and yes their slides probably suck as well. But people were giving borring talks long before Powerpoint or Prezi.
The article refers to an essay written in 1985 that makes a very clear argument that it's your responsibility to make your presentation interesting, exciting and fun, and that above all you must be enthusiastic about your subject. If you are going to give a presentation soon I recommend that you read it.