That's why I recommend the motto "later rather than sooner" -because the audience has to wait for whatever newsworthy or surprise element a slide might have in store for them and gets
the impression that the speaker is in full control and knows
exactly what's coming next.
I illustrated and discussed the point a while back, with video
clips of Steve Jobs getting it wrong and getting it right (HERE).
In his recent speech at the White House Correspondents dinner (above), President Obama demonstrated that he too knows that pressing the
button (or getting someone else to press the
button) "later rather than sooner" is an effective way to
time when to reveal each next slide.
It was also a marked improvement on his use of visual aids
than was to be seen in the slide-pack used in the 'enhanced'
version of his State of the Union Address earlier this year.