No, not Greg Mankiw/Mick Jaggar.
The Chronicle of Higher Ed has an article discussing the various benefits and costs of having actual celebrities teach university classes. The example used is Kal Penn (of "Harold and Kumar Go To White Castle") teaching a class on the image of Asian Americans in the media for the University of Pennsylvania.
My first thought...if a university wants to experiment to find something that works, let them. They bare the consequences of their decisions.
My second thought...Shit! Everybody in the world thinks they know economics and offer up loud vociferous opinions, especially celebrities. Economic ignoramus extraordinaire Michael Moore and protectionist Lou Dobbs could wind up teaching micro principles under this trend!
I'm on the fence, but leaning towards putting more weight on the first thought.