Think about the last time you updated your Facebook status. You probably edited that snippet of text a dozen times to get every word just right. And then, right before you posted it—cursor hovering over the Share button—you likely considered how your friends were going to react.

“People are going to Like this,” you thought. “Maybe I’ll even get a few comments.”

Now, how many times have you run that same internal monologue before blurting out your opinion during a face-to-face chat with your best friend? I’m taking bets on the answer. And my money is on never.

Every time you post something on Twitter, Facebook, Tumblr, or Instagram, you’re influencing—or trying to influence—how the world views you. Each carefully crafted 140-character message that goes out into the metaverse fills a publicly accessible database that defines you to people you’ve never met. In the end, it isn’t who you really are. It’s the hilarious, adorable, fascinating, intelligent, so-worth-Friending version of you. Social media isn’t about having a conversation with people you know. It’s about advertising yourself. It’s not social; it’s media.

Real conversations don’t happen in public. You don’t go to a party and loudly tell strangers about your recent bout of crippling depression. Or the fact that you just can’t seem to trust people enough to make a true connection with a partner. No, the kinds of conversations you have in mixed company are edited for content. You tell people what you think they want to hear.

Mostly that means telling them interesting bits that are designed to make them like you. Like that time you locked yourself out of the house in your pajamas on a rainy night. (You’re so funny and humble! We all just love how you can laugh at yourself!) The world of social media is just like that. Even a closed network (like an invitation-only Twitter feed or a private Facebook profile) is a group of people you’ve decided you want to like you. They don’t want to hear about your irritable bowel syndrome. Not now. Not ever.

Read the Vanity Fair Take

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The idea that we’re having a “conversation” online gets even more absurd as your network gets larger. You might have heard of anthropologist Robin Dunbar. He’s got a number. According to Dunbar, humans are cognitively capable of connecting with only 150 or so people at any given time. In other words, your brain is only big enough to hold personal information about a limited number of people. Everyone else is just noise. Even Facebook agrees with Dunbar, sort of: It doesn’t allow users more then 5,000 “friends.” The assumption is that once you’re linked to that many people, your network is no longer populated by real connections. Your real friend would call you in tears to pick her up from a car accident; your Facebook friend would simply post a photo of her cast and a sad-face emoticon. You feel sorry for her, but you don’t experience the panic that comes from witnessing someone’s distress firsthand.

Dunbar isn’t the only one who believes that managing relationships on a large scale is impossible. In 2009, sociologist Gerald Mollenhorst concluded a long-running study looking at how we manage our real-world social networks. Over the course of seven years, we replace 48 percent of our friends with new ones, Mollenhorst found, though the total number in our network never changes. In other words, there’s only so much room for new people in your life. And you’re certainly not replacing one of your IRL friends—who actually knows you—with some random person who started following you on Twitter.

Those randoms, by the way, end up being a substantial part of our audience. In a study by UK gadget website Good Mobile Phones, which queried more then 1,500 Facebook users, 60 percent of participants said they no longer knew 20 percent of their “friends,” and 50 percent responded that they actually speak with only 20 percent of them. The average Facebook user has only about 130 friends. So, if we’re spending most of our time online talking to people we don’t even know, how deep can the conversation ever get?

Dan Schawbel, a branding consultant, says we are all constantly building our brands online, whether we like it or not. “The Internet is your permanent record,” he says. But while many of your witticisms and clever observations remain for posterity, searchable by Google, the conversations around them are fleeting. The public Twitter replies get replaced by new ones, and comments on your Facebook feed shrink to make room for fresh ones. All that really counted was your initial post and how it affected everyone’s opinion of you.

The best evidence that social media isn’t really about personal connection? Marketers love it. It seems like every business from taco trucks to GE is hoping to use social media to put a personal face on its brand. The truth is, my personal Twitter feed isn’t all that different from @wired, the brand central station of this magazine’s social media presence. We both post links to stories we think our followers will like. We both update with anecdotes about people we know. And we both choose our words carefully before we post them to be sure they mesh with how we want the public to perceive us.

There’s nothing wrong with wanting to have a personal brand. It’s what the Internet is best at. But no matter how you slice it, a social network is a public place. And posting there is like choosing what T-shirt to wear or how to cut your hair: It’s another way to control how the world sees you. You are not your Facebook page or your Twitter feed. They’re just snippets of you. And no one ever had a real, honest conversation with a snippet.

P.S. You should totally follow me on Twitter (@erinbiba). Everyone agrees I’m way more hilarious and adorable there than in real life.

Correspondent Erin Biba wrote about extreme food in issue 19.06.