It's federation that is the problem. Federation leads to fragmentation, which ultimately is a headwind to adoption. IMHO you need a single network that allows people to choose the "channels" that you can view/join and then people that join that channel start hosting and replicating the content. Also, great filtering controls are critical to the success of such a platform.

Not sure if there is really anything attempting to implement essentially Twitter with this model or not? I would be interested though if someone has run across or is working on a system like that.