Snapchat (www.snapchat.com) is a photo or a video, add a caption, and send it to a friend (or maybe a few). They'll view it, laugh, and then the snap disappears from the screen - unless your friend takes a screenshot!
The image might be a little grainy, and you may not look your best, but that's the point. It's about the moment, a connection between friends, and not just a pretty picture.
The allure of fleeting messages reminds us about the beauty of friendship - we don't need a reason to stay in touch.