All of these "disappearing ink" apps are patently ridiculous, they all have demonstrated security flaws, and they completely ignore the analog gap problem.
What are people thinking when they decide to use this crap?
... "Oh cool, look at me, I am a spy... let me send you something sekret, tee-hee I am sure this other dude running this server is totally cool too so you can send me your sekrets back... tee-hee-hee... nobody will ever know"
So many god damned stupid fucking kids walking all over my fucking lawn these days!