I am particularly annoyed by the name "Whisper" for the "25 seconds only" messages: It got me to read on because I thought they interfacing with WhisperSystem's protocol for TextSecure. Because, open protocols, federation and all that. Would have been nice, right?
Well, thumbs down for that.
Also, if you don't trust the other to not want to log your conversation, don't send sensitive stuff. But then again people do seem to like snapchat and thelike, so I shouldn't judge too much there maybe.
I guess it's a slight reassurance, for example if I want to send a password to someone I trust, I could do it with whisper knowing if someone picks up their phone in a weeks time it will be gone.
Also, if you don't trust the other to not want to log your conversation, don't send sensitive stuff. But then again people do seem to like snapchat and thelike, so I shouldn't judge too much there maybe.