The blog post author writes, "Bullet points make information more difficult to remember, especially when the bullet point lists are accompanied with auditory information." And continues,
Dr. Atherton explains that when you accompany a lecture with bullet point slides, your audience will switch between reading and listening. This type of task switching is cognitively exhausting.
(Watch Atherton explain in Learning Technologies 2011 - Dr Chris Atherton - From cognitive psychology to learning design.)
Ethos3's concrete example of transforming a common slide into ones from which audiences will actually learn is easy to understand and quite helpful.