I agree with the author that asking questions about superheroes is going to weed out qualified people (unless the project involves superheroes). When I interview someone, I do my best not to ask questions irrelevant to the job. I don't know why someone would ask a question biased against people from different cultures, etc.
As for whether Dropbox should change its culture to be more attractive to women, that's their choice. They should be aware that their decor might turn off some otherwise qualified people, whether or not they choose to act on that information.
I've worked for and interviewed for Google for about ten years, and our training includes not asking irrelevant and/or culturally biased questions.