oddly enough I was just talking to some friends about this last night. I figure that I've managed to keep my gaming at a safe level gauging by the excellent marks that I had last semester.
But the games are definitely made to get you hooked. Consider my girlfriend - never played significant video games, and has no previous interest or knowledge of the WoW universe. All she has is me talking about it. She tries it out for a couple hours, and already it took a bit of doing to convince her to log off, and the next day she told me she really wanted to play and not study for summer school. It sure didn't take much to get her interested.