Conceptual cameo

As next week's will be my first syndicated column, I thought I'd wade in with heavier artillery than usual. What do F.A. von Hayek, Karl Marx, Benito Mussolini, Madonna and Neal Stephenson all have in common? They all make conceptual cameos, as it were. Ten points for anyone who can name the literary tie-in of the subtitle come Monday. Comments will be welcomed.