Once upon a time, in vanilla WoW, raiding was the line drawn between the casual and the hardcore player. It was a big deal to be in MC/BWL/AQ and ultimately Naxx.
But over the years, Blizzard actively made changes to make raiding be in the grasp of most -- if not all -- of the players who wanted to participate in end game content. PUGable raid instances replaced high-learning curve instances. And there was little left activity-wise to differentiate between the casual and the hardcore player.
But then there was the introduction of Ulduar and its hard modes. My casual guild has yet to actively go after them, despite at least a few being pretty readily attainable with a good crew. It would be lovely to see Algalon eventually, but I just don't have the expectation that enough of my casual guildies would be up for wiping for 3 hours to attain a hard mode kill.
So, does that make hard modes the new line in the sand between casual and hardcore? Are many casual guilds going after the hard modes? Or are they, after killing Yogg, swapping in alts or lesser-experienced players instead?