I read an interesting story written by Deborah Grayson Riegel, who was giving a presentation at the Bronx zoo. In addition to her human audience, there were 20 monkeys outside with their faces pressed against the window, watching her presentation. Each time she advanced her PowerPoint slide, the monkeys would bang their fists against the window. Eventually, she had to let go of her PowerPoint presentation, and stopped changing the slides altogether.
Most of us are not going to be speaking at the zoo, but we will have our own monkeys to deal with - the usual cast of characters known as a difficult audience - hecklers, people causing distractions, zoning out, and generally interrupting your presentation. It's important to be flexible and work with your audience.
Speaking of monkeys... someone recently threw a monkey wrench into my half day presentation training workshop, which was scheduled from 1:00 - 4:00pm. We were told that four of the participants had to leave by 2:30. The program was designed to build speaking skills so the speakers would be prepared to give their final presentations at the end of the workshop. We had to do a quick redesign on the spot - in 5 minutes. My partner and I huddled and came up with a plan. The goal was to give each participant the opportunity to present, leave on time, and still gain enough learning to succeed in their next presentation. It worked.
In public speaking, as in life, we always need a backup plan. Deborah had no choice - the monkeys forced her to stop using PowerPoint. Your audience may be more subtle, but good public speakers pick up the nuances and can change in a moment to better serve their listeners. Technology will fail. And an audience can quickly tune out. We need to be able to go where the current is taking us. That's the mark of a professional speaker.