> That said, I don't know how you would monetize a system like that.
My personal intuition is that the simplest forms of communication (defined as exchanging data between two or more participants) shouldn't be _directly_ monetized.
If we compare to physical communications means and services, there's an obvious yet powerful realization to make: communication is free (from any third-party) so long as it's distributed (i.e. when you and I talk, we take it upon ourselves to spend the energy required to communicate, we don't need a middleman), whereas it becomes a paid-for service when it's centralized (e.g. post office, telephone system, nowadays internet).
Notice that in the physical world, most (centralized) communication businesses are monetizing a more-or-less public container, which operates as a black box for the (de facto) private content. — e.g. package, letter, phone conversation.
Translate this into the digital world: email, file storage and exchange, chats and calls. So far, to my knowledge, most of the popular solutions have been centralized and therefore, monetized (notable exception are bittorrent or IRC, the protocols, widely used as a consequence, but rather nerdy to the general pop, which I think has to do with UX).
Simply put there's a business behind most of the middlemen (Fb, Gmail, Skype…), few solutions rely strictly on tech that anyone can freely operate: you need that central server authentication to reach other users in the walled garden, and neither 'speaks' to others (can't use app X to speak to someone using app Y).
Back to my personal intuition, there is an increasingly higher chance that someone comes up with a decentralized communication system wherein users each bear the cost/energy required to communicate, based on a free protocol (as in beer, it needs not be OSS, although probably should for security/trust purposes).
Think Bittorrent for data specific to communication. The internet in itself, with requests being free (POST GET etc), is such an example of a distributed architecture which you enter simply by leveraging the correct tech; there is no gatekeeper. Blockchains might be another good example of distributed systems (even ignoring cryptocurrencies and focusing on the distributed database tech).
It's a general trend, I think, that we progressively massively distribute technology-based services starting with the most fundamental, the closest to "first principles" for the purpose. Think about printing, how it started with Gutenberg, what a single individual can do today. It takes decades, centuries, these are deeper trend. However, as fast as things go in this day and age, I think communication is just about to be disrupted _forever_ by virtue of massively distributing the means. Just like printers. Or file exchange.