I don't know anything about Mensa first hand, but being a big fan of cut and paste I thought this was interesting:
Mensa is a club whose only requirement for inclusion is a score in the top two percentile on any of several standardized intelligence tests. That said, Mensa is populated for the most part by: (a) lonely people; and (b) financially unsuccessful people desiring verification that there is something worthy about them, ie, their intelligence. Many Mensans just haven't fit in very well with the world at large.