Imagine if you could send a photo to someone else that couldn't simply be captured or saved. In other words, a screen capture wouldn't work and neither would taking a photo of the screen with another camera. One of the first Java applets I wrote solved this problem. But, since then, I haven't seen this technique used anywhere (which probably means there's not much demand for it).
I still think there's a market for displaying photos that can't be captured. But this technique is only a feature... there's not enough for an entire business. I'm just surprised I haven't seen it used. I thought, with the advent of disappearing photos on SnapChat, that it would resurface. My technique for this is still one of my favorite hacks.