Hardcore vs Casual

I had a bit of a rant all over one of SynCaine's blog entries. This leads me to wonder, what makes a "hardcore" gamer? What makes a "casual" gamer?

I humbly suggest that "hardcore" simply means "takes the game more seriously than I do," while "casual" means "doesn't take the game as seriously as I do."

As an example, "everyone knows" that guy whose game is focussed on ISK/hr minmaxing in PvE. That's the guy who has tables indicating the bounties, rewards and completion times for each mission offered by the available agents. That's the guy who has a bunch of agents right next to each other, farming missions for hours a day. That's the guy who declines the missions that aren't as profitable (i.e.: drone missions, anti-faction missions, "Duo of Death", "Buzz Kill", "The Anomaly"), has calculated exactly which ship and fitting is best for each mission, and even has fittings saved for "Nightmare - Worlds Collide - Blood vs Angel", "Golem - Worlds Collide - Serp vs Guristas", "Stabber - Recon (3 of 3)".

Then there's the casual guy. He's got a -1.5 security status because he's usually too lazy to repair his sec standing after low sec roams (or hisec ganks). Today he'll be on for an hour running incursions. Tomorrow he'll be on for a couple of hours "roaming low sec" (which actually means station spinning in a fleet of 8 people while chewing fat and quaffing a brew or three), one day you'll catch him mining ("because I'm bored"), and some days he just doesn't log in at all.

What about you? What is the difference between hardcore and casual? Is there a meaningful dichotomy (or continuum) there, or are these just terms bandied about by people who wish they could formalise the difference between "us" and "them"?