Reminds me of a prof at uni, who's slides always appeard to have been written 5 mins before the lecture started, resulting in students pointing out mistakes in every other slide. He defended himself saying that you learn more if you aren't sure weather things are correct - which was right. Esp. during a lecture, it's sometimes not that easy to figure out if you truly understood something or fooled yourself, knowing that what you're looking at is provably right. If you know everything can be wrong, you trick your mind to verify it at a deeper level, and thus gain more understanding. It also results in a culture where you're allowed to question the prof. It resulted in many healthy arguments with the prof why something is the way it is, often resulting with him agreeing that his slides are wrong. He never corrected the underlying PPP.
I thought about doing that when I was doing adjunct last year, but what made me stop was the fact that these were introductory classes, so I was afraid I might pollute the minds of students who really haven't learned enough to question stuff yet.
