There's a very astute, incisive and philosophically rigorous critique of the Zizek-Lacan critical theory cabal in the sixth chapter of Walter A. Davis's Death's Dream Kingdom: The American Psyche Since 9-11. Davis does plenty of philosophical and psychoanalytic 'heavy lifting' there (in a chapter that also contains one of the clearest critical explications of Lacan I've ever read), so I'll limit this post to a couple of superficial thoughts about Slavoj Zizek's use of popular culture and his position as the reigning rock star of critical theory.
First, Zizek owes much of his Jimmy Page-like status to his use of 'easy' pop culture references to explicate concepts otherwise hidden in the notoriously obscure Amazonian jungle of Jacques Lacan's prose. (Lacan's prose is difficult enough to be worth a parenthetical digression. In one of the footnotes to the book mentioned above, Davis offers this explanation for the difficulties and densities of the Lacanian style: "For Lacan every utterance must gesture in three directions simultaneously: contempt for other thinkers, self-aggrandizement, and the search for opacity.") In Zizek's works, a given theoretical concept--the "obscene supplement," desire, objet petit a--is exemplified via a critical reading of a movie or TV show or some other popular phenomenon. (One of Zizek's more ingenious examples of obscene supplementation involves a deconstructive reading of The Sound of Music that shows how the film's German villains are inscribed as anti-semitic caricatures of Jews while its heroic Austrians are inscribed using the imagery of fascist kitsch.) This is a fun and powerful way to teach Lacan, and Zizek has spent the past quarter-century producing book after book in which Lacan's ideas are exemplified via the works of everyone from Alfred Hitchcock to Halldor Laxness. But all of Zizek's cultural references, high and low, are forced to follow an unwritten but adamantine commandment: Thou shalt only exemplify Lacan; Thou shalt never criticize Him. Once Hitchcock's Vertigo, for example, has served its Zizekian exemplary purpose, Zizek metals his pedal and speeds on to the next example before the complexities of Vertigo (or any other cultural artifact) lead him into reflections that might undermine Lacan or Hegel or Marx. Zizek takes big Quarter Pounder-size bites out of art, but he never allows artworks to bite back. This is the fundamental superficiality of Zizek's relationship to art: artworks are only and always exemplary; they can never be permitted to criticize the Master. (I hereby challenge anyone to find a single example in all of Zizek's work that proves this statement wrong. Show me one time--just one!--when Slavoj permits a work of art, or even a work of kitsch, to undermine or contradict or even critique a basic Lacanian-Zizekian concept.)
With regard to Zizek's Claptonesque status in Theoryland (Tito-era walls all over Slovenia must surely wear the graffito "Slavoj is God," n'est-ce pas?), I think that as a popularizer of Lacan and an original leftist thinker he deserves all the attention he can get. But he should not be considered a 'leader' of anyone or anything (or for that matter, of any Ding). Lacan was arguably a 'leading' figure; while he worked in the wake of Freud and would've had no career without his illustrious Austrian predecessor, his Structuralization of Freudian thought was a powerful and arguably revolutionary move--not revolutionary in Freud's 'Copernican' sense, perhaps, but at least it allowed him to credibly play the role of leader of a recognizable ecole. Zizek, on the other hand, never really rises above the level of Lacanian explicator. He's a born follower, and his academic followers around the world are all playing the time-honored game of Follow The Follower. Like a parody of Lacan's theory of language as an unending chain of signifiers, the Zizekians follow Zizek who follows Lacan who follows Freud, and all their reams of Zizekian signifiers, full of Lacanian sound and fury, signify--you guessed it--nothing much.