My 5 year old LOVES Halo2 online...she hasn't played for a while though. She is a riot with the little headset.
We don't let her go in alone...I will be next to her on the couch (I don't play though) and her uncle is playing in another state, and sometimes her brother or dad is playing.
Regarding World of Warcraft..that is what my husband's life is. I even started a WoW_Widow group at yahoos because of it...and there is another site, GamerWidow.com that covers a lot of different games.
Ahhhh we all need our little outlet to vent hahah.