When creating my gravatar account, I was asked to choose a rating.
This surprised me for two reasons — first, gravatars have ratings? I don’t think I really want to see any X or even R rated gravatars. (And sure, preventing people from seeing what they didn’t want to see is the whole purpose of having a rating in the first place, except until they fed me this page, it hadn’t previously occurred to me that I or anyone else could should or would use gravatars for, er, X rated purposes.) Second, I thought that the ratings below X were trademarked by the MPAA, no?