The irony is that bad crypto like this is worse than no crypto. It is probably more valuable to specifically target users of this phone because they "have something to hide".
They aren't developed in the open (they're opened up in certain releases), but the protocols themselves are open. The server software is proprietary, but the servers don't see any plain-text data.
Even if the protocol guarantees that they don't see unencrypted data? Do you feel the same way about all the internet relay servers between your client and the server?
Full disclosure: I work for Silent Circle and it's pretty damn secure. It's also open-source: https://github.com/SilentCircle