[TazeTSchnitzel]

IIRC Snapchat detects when a screenshot has been made by spotting that the touch event for a finger held down is suddenly cancelled. Maybe they're doing this, then deleting the screenshot?

Though, is it even possible to delete camera roll items for 3rd-party apps?

Edit: Ah, they just notify, not prevent, much like Snapchat:

> They cannot save it to their camera roll; and you will be notified if they ever take screenshots.

Edit 2: The old trick Snapchat used doesn't work since iOS 7. Instead, it hooks a newly-added notification that a screenshot was taken.