When you give a webcast presentation you could opt for also playing a short video. Playing a video during a live presentation when you have your audience in the same room requires preparation / testing. For playing a video during a webcast you should also prepare.
Sometimes not all of your audience members will have a fast enough internet connection and therefore they may experience the video as a slideshow. You could avoid this by having your participants download the video. Ensure this is done in advance. Then you may have the difficulty that not all you audience members will start the video at the same time which results in people not being done with watching the video. You then have to wait till the last one, otherwise you will get complaints that there was not sufficient time to watch the video… This can also be avoided by asking your audience to all open the video file and then count down till 3, 2, 1, to have them all click play video at the same time. By means of this the flow of your presentation will not get disrupted as all will look at the video at the same time.