Gamasutra has an article where many representatives of different Game Developing and Computing Science Companies are talking about World of Warcraft, its success and whether World of Warcraft is Mainstream or not.  Find out for yourself, and read what the experts have to say about this popular MMORPG for casual and hardcore gamers.  Here is an excerpt from

WoW is absolutely reaching the mainstream market. I’m in a guild in WoW where there are many players who are playing their first MMO, and beyond that, playing their first video game ever! For example, my girlfriend plays and she would’ve never thought to buy a video game until trying out WoW. She works at a medical device company, and her female co-workers talk about playing WoW. But then again, WoW is the best MMO out there for hardcore and casual gamers alike. World of Warcraft is a great license also, but to most casual gamers, Star Wars or the Matrix are more notable names. It’s not about the license, it’s about making a great game.
-Tony Dormanesh, Midway