When used right, but often it's used when it's not needed simply to emphasise points being made little more. If your audience prefers to read the slides rather than listen to you then this is where the problems often start. If I am engaged by a presenter I don't really pay much attention to his/her slide content, but they need to be good, hence my point. Of course there are many situations where illustration is needed, as I said in my post above, but often it's slide after slide of bullet points and those are useless.
I have been presenting, guest speaking in business for years, I get invited to events often, sometimes paid and to many hundreds of people, so feel confident of when it's right to use it and when not. You need to be absolutely on your game, confident you can hold the interest of your audience and not need to illustrate but I am dropping slides when able as I find it's well received most of the time. Doesn't work for everyone or all the time of course and it really depends on content.
I have been living and breathing PowerPoint and before that overhead projectors and transparent slides for 25 years, it's nice to dump them now and again!