Sarahah, which means “honesty” or “candor” in Arabic, began as a website tool for soliciting workplace feedback. But it gained popularity after teens embraced a mobile version of the tool, and after Snapchat offered users a way to send each other links to their Sarahah page.

Today, according to Apptopia, it has vaulted ahead of familiar iTunes Store stalwarts like YouTube and Instagram:

The question, though, is how long this is going to last. During a debate, my editor Andrew Nusca and I arrived at a similar conclusion: Not much longer.

You can hear our full views on the Fortune Tech Debate video above, but a short account of our skepticism lies in the fact it’s hard to make money from abuse—which is what apps like Sarahah generate in buckets.

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Even though Sarahah encourages users to “leave a constructive message ;)” (yes, it includes the smiley face), experience shows anonymous apps attract trolls. And the trolls quickly turn the whole environment into a creepy, toxic place that no advertiser wants to go near.

Do you doubt it? Just look at the fate of Yik Yak and Secret, which likewise offered anonymous online platforms for gossip and chatter. The apps rapidly acquired millions of users and gobs of venture capital dollars, but flamed out in part because trolls turned them into cesspools of toxicity.

It’s possible Sarahah is different. As Andrew notes, teens keep expressing a desire for unfiltered, authentic platforms for online expression. While Facebook and Snapchat may have offered this once, those companies are now fixated on obtaining marketing data for advertisers—and in any case, such sites are overrun with older coots like Andrew and I, which might further diminish their appeal to teens.

So maybe Sarahah is the solution. But we think the safer bet is that, by this time next year, the most common reaction to the app will be “Sara-what?”