Comment by mmakunas

You're missing the point. People are realizing that it's probably not a good idea to have every pic you ever take be out there for the world to see. But they still want to share them with certain people. They (rightfully) don't trust other people to delete them (or lose there phone, etc.) and they don't trust the privacy settings of facebook and the like. Given that, having a mechanism for sending a pic and (almost) guaranteeing it is deleted is a compelling use case. Snapchat could certainly fail, but I think the general use case will be enduring.