One Memento is a new photography experiment designed to capture 250,000 single moments. Participants download a one-shot digital camera app from the iTunes App Store, giving them one chance to take a single photo for the experiment. All they have to do is capture an image, or choose one from their phone’s photo gallery, add a comment and share it on Facebook or Twitter. Their ‘One Memento’ will be kept safe in an online gallery for their friends and the world to view. Once shared, the user’s One Memento can’t be altered or deleted - according to the initiators of the campaign, this forces users to think before they shoot and share.