This is definitely coming down the pipe. I think it's extremely imported to come up with an alternative to the existing centralized systems; which I believe primarily exist in order to mitigate spam.

Some people have been working on an interesting solution called StampChat which has a similar topology to email, but the messages are encrypted by default and the spam mitigation is done via sending tokens to the recipient (ala Hal Finney's RPoW) idea.

It's still a prototype, but there is one deployment over here: https://web.stampchat.io

The whitepaper on the protocol is here: https://www.stampchat.io/whitepaper.pdf

There's a faucet here if anyone is interested https://faucet.lotuslounge.org/

We're not doing an ICO or anything, happy to give out more tokens out.