Perhaps not so surprisingly, given that (anecdotally and handwavily, I confess) MtF transsexualism appears to be associated with something like +1 s.d. of intelligence. I've heard super-duper-handwavy explanations along the lines of "male-sized brain with female-style connectivity" but don't know whether there's any truth to them.

And of course there are obvious reasons why open transsexualism might be strongly associated with openness to unconventional ideas and tolerance for the idea of self-modification, both on the part of the individual concerned and of those he/she socializes with. So someone who hangs out with transhumanists might reasonably expect to know a greater-than-average proportion of transsexual people.