I don't have a deep understanding of encryption except that I think I understand the principle of asymmetric encryption where you have a public/private key pair and anything encrypted with the public key can only be decrypted with the private key. This would seem to me to be strong enough encryption to thwart any broad information-gathering type eavesdropping. It wouldn't stop a dedicated attack on a series of communications between two known stations of course. Man-in-the-middle attacks and other types of attacks are pretty good at getting around encryption in these cases. But in terms of "gather everything, put it in a database, index it" I think that would kill this type of collection.
Why aren't there commonly available commercial encryption communication devices? For example, cell phones, land phones, email clients, etc., that detects if the other station supports asymmetric encryption and then exchanges keys and encrypts the data, just like SSL. You would think there would be a huge legitimate (and also illegitimate) market for this sort of thing. And with the power of computers and smartphones these days, there would be no problem with a software-only implementation.
What am I missing?