Snapchat is a new way to share moments with friends. Snap an ugly selfie or a video, add a caption, and send it to a friend (or maybe a few). They'll receive it, laugh, and then the snap disappears.
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.