Strongly reminiscent of this really fantastic talk from Eric Mazur, a Harvard physics professor (and a charismatic speaker!) who was shocked when he discovered the pervasive misconceptions held by his undergraduate students.

http://www.youtube.com/watch?v=WwslBPj8GgI

Mazur describes how he discovered and carefully measured the lack of fundamental understanding among the majority of his students, and how after attempting to address the problem in various ways, he found that a discussion-based, peer-assisted method of working through material was much more effective than more a lecture-oriented approach.