You may not think you’re sharing with many people when using Facebook’s “Friends of Friends” privacy setting, but two degrees of separation actually goes a long way.

According to a new Pew study, Facebook users who share with friends of friends reach an average of 156,569 other people. Granted, that’s the mean average, which skews a bit high due to people who befriend pretty much everybody. But even the median user has a lot of reach, with 31,170 people connected through friends-of-friends.

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Statisticians probably figured this out a long time ago. After all, with the average Facebook user having 245 friends according to Pew, and the average friend of that user having 359 friends, one person’s reach can easily get into the tens of thousands even after you account for overlap. But for me, at least, Pew’s results are surprising, as they are for Gizmodo’s Sam Biddle, who put it this way:

When you think friend of a friend, the IRL analogue comes to mind. Your buddy’s buddy. That guy you met at a bar who seems okay. Your girlfriend’s pals from college. They must be okay people, right? They’re so narrowly removed from you, why not share all your photos with them?

Of course, on Facebook, the definition of “friend” is elastic, and so you may be exposing your life story to people that shouldn’t have it. Fortunately, Facebook doesn’t really promote the “Friends of Friends” option anymore, instead burying it within the “Custom” privacy settings.

But if you use “Friends of Friends,” and are now freaked out by it, you can switch it off by clicking the little arrow on the top-right corner of Facebook’s website, then clicking “Privacy Settings.” From here, you can either press the big “Friends” button, or click “Edit Settings” in the “How You Connect” section to fine-tune your options. Also, next time you’re sending a status update, click the little drop-down menu next to the “Post” button, and make sure you don’t have friends-of-friends selected there.

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