we've had popular and commercial peer or group based messaging for more than two/three decades now, but nothing has rivaled the virality and speed of Facebook, twitter and so forth. There's a difference between propagation in a private network of a handful of people at a time, and the sort of mass agitation of public social news feeds.

If twitter would only allow direct sharing between say, a personal circle of friends, I'd bet you a lot of money that we'd see very different outcomes.

In Myanmar, it was the private network of individuals, resharing posts on WhatsApp. Everyone only shares to their direct friends - but then those friends share with their friends etc. And I don't see how you can restrict that technologically - I mean, you could block share-of-share, but then people will just reshare screenshots (it's already common enough as it is).