Secretive White House Surveillance Program Gives Cops Access to Trillions of US Phone Records

That’s a great question to ask! The biggest weakness of any “mathematically private” communication channel is not mathematical, but simply humans (users): Alice, Bob, and also the channel itself implemented by a human coder Chris.

While we don’t need to be paranoid but as a matter of fact, even assuming Alice does everything right, Bob may be sloppy, saving decrypted plain text in a random place (even uploading his own secret key to “cloud” or something, assuming it’s good idea to have a back-up of important files). Also the channel might have a hidden backdoor, perhaps side-channel, unknown to Chris.

It seems important to be aware of these possible human factors.

Also there is this big problem of metadata (this AT&T thing seems to be also largely about metadata).

[Additionally, though less importantly, most cryptography is based on unproven mathematical conjectures, like y=f(x) is easy to compute but it’s hard to get x from y. Which may be relevant when the one-wayness is based on the difficulty of factorization as in RSA.]

Yeah but can you trust the people you talk with not to install shitty stupid apps

You can't, but the threat exists regardless of what service you use.

Regarding my phone number being leaked, I'm okay with that risk. It's relatively easy to ignore/block unknown contacts and I'm not in any threat should someone discover it. For anyone who absolutely needs anonymity, they may want to wait until user names are rolled out and use another service for now.