It’s a good thing Facebook (FB) bought Instagram.

Because that’s where all of its teen Facebook users are headed.

Yes, FB stock bulls have heard this too many times to care, but yet another survey says teens are abandoning Facebook in droves. Whether it’s to avoid their parents and other adults, too much drama or simply because Facebook isn’t cool anymore, the number of teens copping to using the social network fell of a cliff in the last half year.

Not that it has made a difference to the market or FB stock. For the year-to-date, Facebook shares are up more than 40%. Heck, in the two-and-a-half years since going public, FB stock has more than doubled — even though we’ve heard these warnings plenty of times before.

Of course, that doesn’t mean that this time it can’t be true.

According to a semiannual survey by researchers at investment bank Piper Jaffray, 45% of teens aged 13 to 19 are Facebook users. That’s a shockingly steep decline from six months ago, when the same survey found that 72% of teens 13 to 19 were using FB.

Facebook Less Cool … For Now

Teens are nothing if not fickle, so that trend could do a 180 in the next Piper Jaffray survey slated for six months from now. But if it’s true and it persists, the only thing propping up FB stock might be its ownership of Instagram. (Don’t look now, but that’s the No. 1 social network for teens these days.)

Even Twitter (TWTR) has lost some ground with teens over the last six months, although it’s still more popular than FB. Here’s a look at teens’ favorite social networks, courtesy of Piper Jaffray:

As you can see, from spring 2014 to fall 2014, the number of teens aged 13 to 19 using Instagram jumped to 76% from 69%. Twitter fell to 59% from 63%. Facebook managed to cling to third place throughout 2014, but the number of teens admitting to using the site fell by nearly 30 percentage points.

It’s not great news for anyone holding FB stock, but neither is it worth worrying about — or selling your stake over — either. As noted, Facebook has been hit with these types of conclusions plenty of times in the past and it hasn’t made any difference to results or returns. Regardless of what teens say, there’s no evidence FB is struggling from the loss of this key demographic.

Everyone (including Facebook itself) knows that FB’s user base eventually will stop growing. After all, there are only so many people in the world. Buying Instagram, WhatsApp and Oculus Rift are just a handful of ways that FB is positioning itself to remain relevant with teens — and older users too — as the pool of social media users gets saturated.

The latest survey data may be alarming on the face of it, but FB stock still has a long way to go before it’s uncool.

As of this writing, Dan Burrows did not hold a position in any of the aforementioned securities.