Perhaps the survey is heavily influence by what people are willing to post on Facebook, or what there particular FB circles tend to emphasize? For example, there might be a lot of people in DC who work at government jobs and who probably don't want their super-hero freakiness talked about at work, or in a committee meeting.
It would also be influenced by the other things people have to post about, which in some areas would be food, surfing, night life, and whatnot, while people in pretty boring places would be more likely to post about Star Wars.
A better methodology might be to conduct a poll where all the questions are sci-fi obscurities.