These aren’t hipsters. (Paul Sakuma/AP)

On Urban Dictionary, Instagram is defined as “Every hipster's favorite way to make it look like they take really classy pictures when really they are still using their phones. Yeah, you might look really cute/old school/vintage/retro, but it’s still a cell phone picture.”

Now everyone is dashing for the exits. Facebook might just as well have posted a giant banner screaming, “INSTAGRAM JUST SOLD OUT AND WENT MAINSTREAM.”

And nothing attracts hipsters like the news that you just sold out and went mainstream.

What will become of Instagram?

Beware of Greeks bearing gifts, free lunches and people or things that describe themselves as “quirky.” Invariably, there is something the matter.

Instagram has “quirky” in its own self-description. Whenever someone uses it, it informs you that “Kate is using Instagram — a fun & quirky way to share your life with friends through a series of pictures. Snap a photo, then choose a filter to transform the look and feel of the shot into a memory to keep around forever.”

Maybe it makes sense. Hipsters, as a class, are people desperately striving to be effortlessly quirky.

Being quirky takes a great deal of work, if you’re really serious about it. Once, it just required you to don the occasional pair of bloomers and bicycle around talking to potted plants. Now it’s a full-time commitment. You have to spend all your days in meticulous 19th-century military uniform, or you will be Just Like Everyone Else, a fate worse than a lifetime of drinking tepid PBR.

You can’t walk into buildings through the doors (too mainstream) or listen to music another human being has heard even once (so 1990s) or wear any clothing that implies you are aware of your general body type (so limiting). Regardless of your age and sex, you grow a beard, don thick-framed glasses, and pour your figure into skinny jeans and plaid. Alternatively, you dress like a circus character, inspiring blogs like “Halloween or Williamsburg?”

Some question whether or not these beings actually exist. After all, one of the most telling marks of a hipster is a violent hatred for hipsters and fervent denial that you are one.

The only thing that unifies all hipsters is a terror of being “too mainstream.” If a hipster falls in a forest . . . you probably wouldn’t have heard of it.

But Facebook defines mainstream. It is the place that Everyone Knows About Already. No wonder people are fleeing Instagram. You are supposed to be that effortlessly cool person who finds things before they Become Known And Ruined. This ruins all that.

Still, this raises another point: Clearly Facebook thinks that hipsters have value.

This seems odd. After all, they don’t have televisions. They only shop at five places — Urban Outfitters, American Apparel, Etsy, Goodwill and Somewhere Else You Definitely Haven’t Heard Of. And once you’ve identified the place where they all congregate, they’re gone. You can’t locate and mon­etize them at the same time. They’re like Schrodinger’s Cats, in ironic grandma sweaters and thick-framed glasses. The instant you find a bunch of them pullulating around something, that’s the surest sign it’s gotten Too Mainstream.

Facebook has made the rookie mistake of many people who stroll into Urban Outfitters and buy everything in stock, in an effort to appear Suddenly and Effortlessly Hip. It doesn’t work that way.

How does it work?

I’d tell you, but you wouldn’t get it.