Let's take a poll. If you consider yourself "casual" raise your hand. Yes, even you in the back-and you thought that webcam was off (and put some clothes on for God's sake).
Ok, that's quite a bit of you. Now, if you play more than 20 hours a week keep your hands up.
That's what I thought.
At the last two Dragon*Cons I've asked that same question on my panels. The numbers come out like this: 90% of the room raised their hands at the first question and 80% of them kept their hands up for the second.
You are not a casual gamer if you fall into that spectrum. Since I am laughably a games journalist, I am eminently qualified to use the word the industry uses to define "casual gamers": Peggle. We also have a word to describe people who play Peggle too much, but since AOL owns us I probably can't use it here.
When you wonder why Blizzard doesn't do enough for the casual player, or why they focus their attention on the hardcore raider, the answer is simple: Blizzard doesn't have a clear delineation between the two groups any more than you do. It used to be that casual players refused to put in the time to get ahead, while the hardcore raiders were a bunch of catassers who had no lives. WarCraft has drastically blurred those lines. Robin Torres wrote an excellent piece on the differences between casual and raiders here. Let me say I agree with her, but she was a tad too polite.