[imglorp]

I would argue the biggest downside to encrypted email is the sender, recipient, date, and size are known to all intermediaries.

First of all, sometimes knowing who you talk to is more important than knowing what you say. Traffic analysis lets you draw all kinds of conclusions.

Secondly, there are two parties, so double the chances for rubber hose cryptography. An opponent can approach either party and ask for details, so both parties are trusting the other can't be broken by the opponent.

Of course, we should all be encrypting everything anyway, no point in giving out free message bodies.

[dexterdog]

If you don't trust the other party you should not be sending him sensitive data. He has to be able to see it so of course he will be able to reveal it.

[alephnil]

It is not that you don't trust your party, but that anyone with access to the servers or network between you can learn about who you are communicating with and when. Such metadata are often more useful to use against someone than the actual content.