Chris Bateman of Only A Game has spent a not insignificant chunk of time talking about the 'hardcore/casual' divide — especially in terms of discussing the accuracy of such a distinction. As he points out, more complex models of how people like to play their games are simply too unwieldy to be of use for general conversation; still, a lot of the ideas about what makes a 'hardcore' player versus a 'casual' player don't necessarily stand up when looking at certain (admittedly self-reported) studies, like the DGD1 & 2 questionnaires:

Most of the findings in this regard are trivial. Hardcore gamers rated themselves higher for the importance of all the emotions we inquired about (and all these findings were highly statistically significant) – which is to say, Hardcore gamers were more emotionally invested in their play, or at least more likely to rate the importance of any emotional factor in their play higher. Hardcore gamers also rated themselves higher on every aspect of game literacy or player skills in the survey (and these results were even more statistically significant). Finally, Hardcore gamers were more interested in games of challenge, structured play (Caillois' ludus) and games of escapism (acting out in a virtual world) – all of which broadly validated the findings from the earlier DGD1 survey. But these results obscure something interesting about the players who self-identified as Casual. Firstly, Casual players still play games very often. 81% of those who self-identified as Hardcore said they played videogames everyday, but 49% of Casual players also said they played everyday. Hardcore players gave themselves high marks in game literacy (more than 95% of Hardcore respondents claiming the top two marks, and about three quarters the very top mark), but Casual players didn't exactly rate themselves low on this (around 85% of Casual respondents claimed the top two marks, and roughly half the very top mark). So while some of these Casual players might be mass market players, many of them are highly game literate players who play videogames every day. (Incidentally, those who were unable to choose between Hardcore and Casual looked remarkably similar to those who self-identified as Casual).

He goes on to say there is a gap between 'casual games' and the so-called 'casual player'; he ends by asking if there's anyway to redefine our terminology in a way that is useful and usable. I think an 'either/or' split is here to stay, at least for a good long while, if for no other reason than people like clear divides — even if they don't correlate to reality. Redefining Hardcore & Casual [Only A Game]