An interesting tidbit dredged up from Raph Koster's presentation at the Austin Game Conference comes via Wonderland: most gamers are introverts. Pardon us while we gasp in disbelief for a few minutes. Koster claims that most gamers fall into the Myers-Briggs types INTJ, INTP, ISTJ and ISTP. With INTJ being a classic scientist, and INTP a classic programmer, it seems as if games really are designed by nerds, for nerds.
As Alice points out, what would a game designed by an extrovert look like? How are those of us who have Myers-Briggs types beginning with E catered for by modern games? Perhaps we're more likely to head off to the pub and pay someone else to level our MMO characters -- perhaps we're more drawn to social or casual games -- or perhaps we just don't play at all.