Joe Kukura

To those who have been burned by Facebook privacy settings before, revenge is a dish best served cold -- on Christmas Day, and in the kitchen of Facebook CEO Mark Zuckerberg. The Zuckerberg family did Christmas together, a family moment of which we see can see a snapshot above. The photo was posted to Facebook as "private" by the photographer, who did not realize that "private" photos still show up on the newsfeed of everyone tagged in the photo, and therefore can end up plastered all over the Internet within hours.

This is funny, because the photographer is also the Facebook's former marketing director, and the current sister of Facebook CEO Mark Zuckerberg. Even top Facebook executives do not understand how Facebook privacy settings work!

The Zuckerberg family Christmas photo went viral shortly after being snapped by Ms. Randi Zuckerberg -- Mark Zuckerberg's sis, former Facebook marketing director, and currently the executive producer of an awful reality show. Ms. Zuckerberg posted the photo as private -- but like a good Facebooker, she tagged everyone in the photo. Everyone in the photo included Facebook CEO Mark Zuckerberg and other members of the Zuckerberg clan. The private photo showed up in the newsfeed of everyone tagged, and everyone who subscribes to Randi Zuckerberg's Facebook feed.

One of Ms. Zuckerbergs followers -- not a friend, just someone who subscribes to her feed -- saw the photo and tweeted it. Callie Schweitzer, another marketing director type at Vox Media, tweeted the photo with the message, "@randizuckerberg demonstrates her family's response to Poke".

Poke is a new photo-sharing app that Facebook rolled out last week. The suddenly-viral photo shows the Zuckerberg family using this new app, and the app will get plenty of free promotion because of this quasi-scandal. Hmmmm, how conveeeeeenient.

Promotional considerations aside, Ms. Zuckerberg was none too pleased to see that her private photo had been made public -- even though it was public because of her own Facebook settings. She angrily tweeted back to Ms. Schweitzer, "not sure where you got this photo. I posted it to friends only on FB. you reposting it to Twitter is way uncool."

Nonetheless, it was Ms. Zuckerberg's privacy settings that were way uncool. Ms. Schweitzer is friends with Arielle Zuckerberg, who was tagged in the photo, and so the photo appeared on the newsfeeds of anyone who is friends with any of the Zuckerbergs appearing in the photo.

Upon realizing this, Ms. Zuckerberg remained unpleased. "Digital etiquette: always ask permission before posting a friend's photo publicly," she tweeted. "It's not about privacy settings, it's about human decency."

It's unfortunate that Ms. Zuckerberg's private family photo became public -- but then again, this is the same Randi Zuckerberg who last year said in a panel discussion, "I think anonymity on the Internet has to go away." In her case, it just did.