I'm sure it's a question that people will have and the answer is that it's simply because that's what I use for everything. Of course, the exception to that is Xbox Live where I use Cannibal GWJ due to Microsoft's craptacular handling of migrating old accounts from the original Xbox to the 360.
The name came about back when I was in the Marine Corps. My roommate gave me the first portion due to my love of cannibal and zombie movies. So I used the name for a while online; but with such a common word I kept bumping into others with the same name. Due to my hatred of simply adding a number to the end of a name, I decided that I needed to add another word in there.
I really like alliterations so that part was set. I was sitting around the barracks and brainstorming with my roommate and I just happened to have a book by Aleister Crowley sitting out at the time. So that's how the name was born.