More to the point, this "killer feature" is easily cloned by a competitor

(And every time I mention that about Uber on HN, people point out that they can get Uber in any city in the world, so why would anyone who never travels use anything else?)

Snap had first mover advantage, which is nothing to scoff at.

This doesn't really agree with

> The problem is that this killer feature is easily subverted

Let's let one company implement the feature before we decide it will be easy for competitors to implement it too.

The feature is fundamentally impossible in exactly the same way as DRM, because it is DRM. You're sending someone a bunch of data and saying "now, you promise not to look at this, right? Except once."

Snapchat takes two approaches (that I know of): First, they don't stop it, but the messager is supposed to be notified when it happens. They know this doesn't work and can't work, though; avoiding screenshot detection isn't even considered a reportable bug. (see https://hackerone.com/snapchat )

Second, they have a legal barrier, in that using a third-party client to communicate over Snapchat violates their terms of service.

Notably, neither of those makes the messages any more ephemeral. This makes sense, because stopping people from recording messages that you send them is not an achievable goal. Barring some sort of supernatural influence, it's no more achievable for Instagram than it is for Snapchat.