For all the trashing e-mail gets on HN, it is a successful, and ubiquitous, decentralized peer to peer communications medium. It seems like that kind of thing

For all the trashing e-mail gets on HN, it is a successful, and ubiquitous, decentralized peer to peer communications medium. It seems like that kind of thing stands little chance of taking off today where single-entity walled gardens are the norm.