I stumbled upon this user who had this ¿pornographic? gravatar (Warning, not safe for work):

http://www.gravatar.com/avatar/07ded368f8cbe358ce04c259a3cd8236?s=500&d=identicon&r=PG

(Note that the Gravatar rating system seems to have failed in this case.)

While I, personally, think that such pictures are swell and would love to see them be allowed, my guess is that Stack Exchange sites want to maintain a more "family friendly" image? But I don't see a way to flag user profiles or gravatars.

So, appropriate action when such profiles are spotted?
Time to sue Gravatar back to the punch-card era?