This is the expectation I think people need to get over. If you are sending your data to a third party unencrypted, even if that third party is Facebook, you have just published your data, no matter what expectation they might have set. Even encrypted data will likely become public at some point if it is stored indefinitely as computing power increases and quantum computing and further advances become common. As long as we use the Internet with the expectation that everything we send is only temporarily private at best, we will be fine. The idea that we can share privately with a select group on a public network is really something like a delusion, even if you are the NSA!

We still can and should develop private and secure communication protocols like DIME, but nobody should ever expect a hosted communication service out of their control to be private.