Today I got a form letter from Google, alerting me that Google had detected "adult or mature content" on LibraryThing. They gave one example, the LibraryThing.fr page for the Library of Congress Subject Heading (LCSH) "Erotic stories." No doubt some algorithm caught a few keywords, like "sex" or the common porn-word "Lolita" (it's a book, guys).
Also, I got the first real "spam" on this blog with some energetic "anonymous" poster who kept sending me the message "Lolitas are hot!" I would recommend that he (and I assume it is a he) read "Reading Lolita in Tehran", but I doubt he'd get it.