I haven't yet read the article (I will I promise.) but I wonder though out of everyone they questioned, how many had been involved with computers in the earlier years (punch cards, 80/88s, etc...)
I wonder though, (and ladym01 may have already heard about this) is there a relation towards specific activities improving brain function. Locally an Alzheimers group is utilizing a storytelling method as a form of brain exercise and therapy for a group, and its been incredibly successful. Now, there may be a connection between what brain functions that therapeutic activity is accessing, that correlates to the brain area that WoW players are accessing - that is yielding these positive results.