Isn't there a rule in the Big Ten that head coaches can't go from one Big Ten school to another?
No - the same "myth" exists in recruiting. It's a courtesy shown, provided it doesn't impact your own self interest...in other words - if they could put the Huskers in the tank for 2-4 years while we find another Bo, and at the same time grab one of the hottest up and coming coaches in the game...they'll be doing it. Hate em if you want, but they'll beat you almost every Saturday and in the end that is what really matters.
(it's a non-issue because it won't be happening, though hypothetically speaking...)