World of Warcraft's Success Hurting the Industry?

Australian website BigKid has published an article entitled "The Dangers of Monogamey", in which they explore the possibility that World of Warcraft's success could be causing fewer games to be purchased. A snippet:
I guess this could be considered a rant but I'd prefer to think of it as an observation that possibly deserves further investigation or at the very least discussion. Could a game be so successful and so addictive that it ties up a big enough segment of the potential game buying public to negatively impact the gaming industry as a whole?