I am not especially a Snapchat fan. It is largely used by people who want to cover their tracks, whether they are criminals doing deals, terrorists making plots or (most commonly) people exchanging inappropriate photos. Yes, I realize that some people use Snapchat for perfectly innocent reasons, but that is not the driving force behind its explosive growth.
It is the perceived "erasing" capability of Snapchat that draws users. As we already know, there are programs that can bypass Snapchat's erasing by letting you open Snapchat messages in those programs, where you can keep the messages as long as you like. And messages are sometimes recoverable forensically as well.
Snapchat has grown so fast that its fairly small band of employees have probably not paid a lot of attention to security. So it wasn't particularly surprising that it was reported last week that some 4.6 million Snapchat user names and phone numbers had been compromised. At least one commentator called Snapchat's attitude toward security "nonchalant."
There are now a lot of these "disappearing photo" apps - even Instagram has gotten into the game.
But beware - not all the promises these apps make can be believed. The best advice is old-fashioned: Assume that what you send will live forever - if you're ok with that, hit 'send' - if not, don't send it. I predict we will hear many more stories about photos that were supposed to vanish but - whoops - did not.