Microsoft has filed a patent application that allows users of a dating site to indicate hidden interests. A user can then find matches based on these otherwise unseen preferences.
As the patent says:
"For example, an ambitious professional is not likely to divulge that he likes, say, comic books, even though quite true. Appreciably, certain affinities especially those relating to fringe interests, eccentricities, or topics about which there is a common misconception or very little mainstream familiarity or understanding are generally omitted rather than included in conventional descriptions."
I'm guessing this is quite useful for interests for which the acronym 'nsfw' was invented.