When it comes to "just being themselves," the cast of the Jersey Shore appeal to this above all. Part of this relates to the show's overall concept, which amounts to the merchandising of "lower class" ethnic personalities; specifically, those whose self-regard is "out of line" with their social standing. But the cast are plausibly genuine in many ways, and I think any good reality television producer would want it this way. Edited spontaneity from their stars is just an easier prospect than elaborate coaching or other forms of micromanagement. Naturally, we have already taken into account the unnatural environment in which the cast are expected to live, and considerable, if unseen, interference run by the crew in order to achieve broad outcomes.
The individual personalities within the cast are no different than many people I know; in an important sense they are no different than me. Of course, I am also different in many ways -- but not in any sense that I consider important. I don't care if people want to spend their time working out or getting tan; is that better or worse than how I spend my time? If the argument is that these people are petty and self-absorbed and spiteful -- I am all of these things, too! As hard as I try, it's very difficult to find an angle where the "notorious" cast of the Jersey Shore are intrinsically more awful than me or anyone else I know, especially when we accord differences in behavior to divergent experiences, opportunities, and privileges -- i.e. to advantages which US society hardly supplies in an even-handed way!
The cultural attributes of the cast are of course meant to be signifiers of a "lower class" that we should regard as important. We're supposed to be able to sum up the worth of an individual just by looking at how they dress or hearing how they talk. This is deeply ingrained in us, and, from the vantage point of power, its utility stems from the disincentive it provides anytime we feel tempted to meaningfully relate to another human being.
Whatever conflicts transpire between the cast members themselves or between themselves and others, the first thing I take from the whole experience is an awareness that the Jersey Shore is trying very hard to tell me what to think about individuals on the basis that they fall into established social categories that I never found compelling in the first place.