Which of these is an acceptable cultural behavior for most Americans? A. Standing for the national anthem
B. Singing while eating in a public place
C. Driving on the left side of the road
D. Dancing during a church service

An informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.