On one hand, keeping slides simple and avoiding "eye charts" clearly makes for better readability, and reduces the risk of the presenter "reading from the slide."
OTOH, a set of slides like that is utterly useless after the fact, unless it's accompanied by a transcript. Both audio and video recordings require serial attention for 15/30/60 minutes that I typically will not have, and I certainly can't see doing that to anyone else.
A question to the assembled: If you make "Presentation Zen"/"Merlin Mann"/etc. low-text high-concept slides for your talk, how do you make sure your presentation is accessible after the fact?