If I may share some thoughts...

To help narrow down your candidate(s), you may want to clarify what you mean by pre-WoW multi-boxing. I think you will wind up getting a lot of responses from people who multi-boxed because they saw somebody else doing it, tried it and fell in love with it. I'm not saying that those people did not become very good or efficient at it...I'm only suggesting that they were presented with the idea rather than forming it for themselves. I don't want to flood this thread with arguments saying "Well...I came up with multi-boxing on my own...", because I know there are lots of you that probably did. There's just more people that didn't (myself included).

I think it boils down to personality traits. Individualists. A person that strives to be self-sufficient. Someone who subconsciencly seeks out the "best of both worlds". Cross that with the type of person that you would see playing several hands of black-jack at a casino, or multiple games of on-line poker. It's not necessarily to increase personal wealth or gain, but more of a compulsion to keep themselves entertained at all times.

I don't fit this personality trait. I starting multi-boxing after seeing other people succeed at doing it. I did it to gain an advantage over a single player. I would certainly agree that I would not make a good interview subject but I did a college research project similar to this topic.