Is it ever OK to lie for skepticism? I would say yes, under very specific circumstances... like when you're teaching students to think critically:
“Now I know some of you have already heard of me, but for the benefit of those who are unfamiliar, let me explain how I teach. Between today until the class right before finals, it is my intention to work into each of my lectures … one lie. Your job, as students, among other things, is to try and catch me in the Lie of the Day.”
This was an insidiously brilliant technique to focus our attention – by offering an open invitation for students to challenge his statements, he transmitted lessons that lasted far beyond the immediate subject matter and taught us to constantly check new statements and claims with what we already accept as fact.
This is a wonderful story, and I think makes an effective teaching method. And it forces students to pay attention... while making them eager to do so! Read the whole thing; you'll get a smile from it.
Tip o' the tweed jacket to Craig Temple.