[TL;DR] In-browser, Cryptocat for email-style communications, using bitcoin compatible address to identify endpoints.
- When PGP is too much hassle and you just want to click on a link to access your messages from anywhere and with peace of mind.
- When you might also want to perform bitcoin transactions as well as chat!
[Scenario 1] Getting a private message 'channel' for advertising campaigns
- Bob often wishes to publish adverts for the services he provides, when he needs to find someone to fill a job position, or if he wants to find a new flatmate, sell his car, etc. He does this using twitter, public forums or perhaps on printed flyers
- He obviously needs interested people to be able to contact him back
- He wants to keep all related communications together - he used to setup dedicated email addresses for this very purpose and put a different one in each advert.
- But now he is becoming privacy aware and is sick of having his personal emails in plain text on some server
[Scenario 2] Secure communications for email-style messaging
- Alice and Bob become friends on twitter and start sending each other messages from time to time.
- At some point Alice becomes wary as the conversation could 'cause offence' to their government.
- She suggests that they continue over private messages.
- She goes to the online service/plugin and generates an identity, giving Bob her public key.
[Silly Scenario 3] Hiding the existence of your PM address in a public communication!
- Some websites try to lock you in to their platform and will not let you exchange contact details with other members. Email addresses will be filtered out of posts you make etc
- Provide different 'encodings' for your public key, so it could be written in multiple ways and easily hidden in a message.
- Simple steganography could be used to hide your public key in some ordinary looking text!
So this could be realised as an open source client + server project.
Any one could decide to host their own PM service. The app would be sooo easy to deploy, you could have it running on your Openshift/heroku instance in seconds.
Also chrome plugins / mobile apps could also be created, which could be more easily trusted through code signing.