“Pix and It Didn’t Happen” by Nathan Jurgenson in The New Inquiry.

“A photograph is made of time as much as it is of light — a frozen shutter-speed-size gap of the present captured within a photo border. Despite this, photographs have always been a way to cheat death, or at least to declare the illusion of immortality through lasting visual evidence. There’s always the possibility that the next photo you take will one day be lovingly removed from a box by some unborn great-grandchild; the Polaroid developing in your hands might come to be pinned to someone’s bedpost in posterity. To update that to more contemporary terms, your selfie on Instagram might be a signpost for the future you of what it was like to be this young.
On Snapchat, images have no such future. Fittingly, its logo is a ghost.
By refuting the assumption of the permanence of the image, Snapchat is a radical departure. It inaugurates temporary photography . . . “