True, but (at least for now) planting a listening device requires significant effort and a warrant. Chances are they will have to be pretty interested in you before going through that kind of effort/expense.

Storing and sifting mountains of data and metadata from everybody, and mining it and mapping it, just waiting for somebody to do something wrong is just too tempting to resist.

That said tho, I tend to believe that most encryption is crackable due to mistakes made during implementation, or mistakes made by the user. In a cryptanalysis class I took my mind was blown by how easy it an be to decode cipher text using simple statistical analysis, especially if some of the plaintext is known.