The concept of being un-self-aware in terms of culture, fashion, or even ideology. Perhaps an impossibility in modern culture, at least since the advent of the Age of Irony and the growing cultural stratification that drives the Corporate Culture Industry. --It is simply impossible for many people to enjoy themselves without placing their enjoyment in a larger social or marketing scheme (I guess I should really limit this claim to those in my peer demographic: the 18-35 year olds). Take music for instance. 'What kind of music do you like?' is often asked as a means to gauge a person's social placement. The answer most often given is a list of bands or some pop genre (ie, 'Anything but Country.'). How would this question have been answered in the 18thC, I wonder. 'Oh, I like counterpoint', or 'Anything but Slavic dances, though I do enjoy a good Polonaise.'
Nobrow is not to be confused with the Lowbrow, which is most often a self-conscious celebration of sex, drugs, and rock-and-roll. Nor should Highbrow haughtiness be considered a sort of transcendence of culture and therefore nobrow.
In my own experience, every example of what I consider nobrow involves something foreign to American culture--such as the taco stand around the block where you can get extremely satisfying burritos if you know how to speak a little Spanish. Is there any area of the American experience untouched by Popular Culture?