Sounds like a new product; just integrate your pgp public key into your facebook profile or something. It'll be here in like a year or something. Geez, why the constant downvoting?

Distributing your public key with your facebook profile is fine, but that won't teach (much less convince) your friends to use it.

Perhaps you could wire up some sort of "facebook app" that would have people talking to you encrypt their messages to you with your public key, but I doubt you could really implement that in a way that would prevent facebook from getting the plaintext (or at least make me confident that they could not). You would also need some sort of browser-side extension to decrypt, or have to copy-paste the messages to decrypt.

Right. So who do you email if no one can read it?