Read the news this morning: Facebook is testing Snapchat-like disappearing messages in France
Well, if you're too slow to read the message, you can always ask the NSA for a copy :).
False security. If this would be of any good, except that you can't read the messages again. It's like writing a letter that gets read by anyone, copied from the authorities, the giving it to you and burned in the given amount of time.
People can easily be tricked these days... *sigh*