The only thing close that I can think of is BitTorrent due to the distrubuted infrastructure, but that's quite impractical to duplicate in this context (how can browsing the content contribute back to hosting and storage automatically?)
In an ideal world I agree, but that's not where we live.
Email and the Internet won because the sector was competitive enough that no one service had enough market clout to not offer e-mail. Once some people got e-mail accounts, other people wanted to e-mail them, and threatened to move off the services that didn't support it in favor of services that did. That scared the online services, so rather than lose, they all started offering e-mail themselves, until they lost anyway.
If you want open social-networking platforms, the solution is to make the market competitive enough that no company can afford not to be open. Usually that'd involve choosing to use the smaller players until they're big enough that no one company is gigantic.
Most of the UKs email over uucp came in via the ukc gateway and IIRC I think I was charged something like 4p/1K for email that was international at that point. From memory my usenet feed came via a US bank in the City and was over a telebit trailblazer modem.
By 1990 I'm pretty sure that cix,MCIMail and Compuserve all at least had gateways to SMTP mail and within a few years it all became more more transparent and free.
We'd need some sort of DNS-for-handles in order to implement something similar for a new protocol, unless you want your handle tied to a domain (in which case you've just remade email with a RESTful API and a length limit)
I don't know of any standards-based activity discussing a twitter-like capability but multiple interoperable implementations, open and closed source, free and for money, provides an 'ecosystem'.
I would contrast an ecosystem to a platform. A platform is owned or controlled centrally whereas a successful ecosystem isn't. A well-managed platform ultimately provides the most benefits to the platform owner whereas a successful ecosystem provides the benefits to the most successful entities within it, a playing field to compete within.
The issues here are open standards, open protocols and the small matter of who pays for the upkeep of the infrastructure necessary to provide the service. Tired, Maoist-style sloganeering is merely making a noise.