While I like the UI and such, the principle is basically flawed, as users had to implicitely trust the server administrators, their hosting providers and their

While I like the UI and such, the principle is basically flawed, as users had to implicitely trust the server administrators, their hosting providers and their CA (assuming https). Even iMessage offers a better trust model - you only need to trust apple, and, if what apple says is true, messages cannot be read by apple nor anyone else. It could be a different thing if the service was installed locally, i.e. under the control of one of the participants in the information exchange (and then the "burn after reading" feature is pointless). If a user would really want to pass along secrets without those things she should use XMPP/OTR instead (i.e. pidgin/adium). Which is really not that hard to use.