One of the most important realisations necessary for media (& cultural) studies is that authors and their intentions are secondary concerns (or more likely utterly unimportant). There are several reasons for this but they are best (first) summed up by Roland Barthes (Foucault's analysis of the problem would be the next step).
For Barthes (and thus for us) the problem of the author emerges out of the great insights of Structuralism. Levi-Struass, Propp, Todorov, and Barthes himself (amongst many others) showed that there were deep underlying structures in human societies and cultures that were universal; they appeared every where there were humans. These universal structures were also present in narratives; plot elements, character types, discourses, etc, are distributed across and are to be found in all societies & cultures. It follows from this that 'authors' are everywhere only re-figuring and/or re-arranging pre-existing elements rather than creating 'new' things ex nihilo.
More importantly still it follows that the theoretical insights we apply - from semiotics, structuralism, etc, - are more important than authorial intention because they concern themselves with context and reception and 'authors' do not.