It's always the epigones isn't it? Those annoying intellectual pygmies who take the thought of the master too seriously and try to extend and develop it. Obviously, not being masters they always get it wrong and even if they should by some miracle get it right they are merely unoriginal. There is something that I find highly distasteful and deeply suspicious about such lines of argument - I think that I've only once used the word and then it was to state that various thinkers were extending an existent line of thought in the original thinker.
A number of more critical points could be made about such arguments. First, it's often a useful way of disavowing the attack, or picking on the weak (pick on someone your own size). What's also interesting is the refusal to 'name names' - again I'm not calling for gratuitous insult but what always used to annoy me about assaults on "postmodernism" was that it was always "postmodernists say this", who? where? and analyse why they are wrong. Second, we could take Žižek's Hegelian point that such "realisations" are part of the original theory. Stop searching for supposed deviations and treat Bourdieu's Secret Admirer in the Caucasus as part of the unfolding of Bourdieu's theory. Third, how would we make sense of Badiou's concept of fidelity without the epigone? Of course the epigone is taken as meaning 'lesser' or 'minor' follower, but why should we regard it as necessarily something to be treated as negative? Of course we could perform a Deleuzian re-reading of the minor as one place to start, and we could also interrogate the implicit concepts of originality and novelty at work here (as well as mastery).
That said, obviously we do need ways to distinguish good work from bad. I'm not for some levelling, but rather a sense of refinement and probity in these kinds of accusations / arguments. Trying to think of positive epigones its interesting that my immediate thoughts are of psychoanalysis and marxism - those two strange discursive fields in which to return to the original texts ‘constitutes an effective and necessary task of transforming the discursive practice itself’ (Foucault). Still, in psychoanalysis Ferenczi, Winnicott, Lacan, or in Marxism, Benjamin, Lukacs, Bordiga (to choose my personal favourites from long lists) suggest 'epigone' could be a category to be re-valued (as Dave Beech and John Roberts have done with the 'philistine'.
Having been an epigone (of Derrida should you be wondering) and never being someone who will reach the dizzy heights of 'master' then I would say this.