Edward Tufte, writing in The Cognitive style of PowerPoint:
[Powerpoint] convenience for the speaker can be costly to both content and audience. These costs result from the cognitive style characteristic of the standard default PP presentation: foreshortening of evidence and thought, low spacial resolution, a deeply hierarchical single-path structure as the model for organizing every type of content, breaking up the narrative and data into slides and minimal fragments, rapid temporal sequencing of thin information rather than focused spacial analysis, conspicuous decoration and Phluff, a preoccupation with format not content, an attitude of commercialism that turns everything into a sales pitch.
Tufte goes a bit over the top here (I'm not sure that the word "Phluff" needs to exist) but in general I tend to agree with his argument here. From later in the piece:
Many true statements are too long to fit on a PP slide, but this does not mean we should abbreviate the truth to make the words fit. It means we should find a better way to make presentations.