I can't think up any plausible social ones

The first thing that came to mind on seeing Kaj Sotala's list is "ah; these are people who like to have fun and think about cool things". But that's more of an indication that I've internalized this clustering of interests, rather than an illuminating hypothesis.

I notice that the items in Kaj_Sotala's list all have in common that they're not plurality orientations in society. That is, a non-plurality of people are transhumanists, a non-plurality take the Pirate Party seriously, etc. In that case, they might all be partly due to a contrarianism/non-conformity trait, a trait which would probably be socially influenced.