I have been placing some thought and effort into this topic also.
The BtcFn (Bitcoin on Freenet) project was my first effort to allow Bitcoin to be run on a darknet. https://www.bitcoin.org/smf/index.php?topic=2312.0
Freenet is designed to be a scalable darknet.
Overall social networking is how anything is ever done. However face to face communication is the most effective, as it is best to trust your real life friends.
The problem with Freenet is that it's not really a darknet, but an anonymous datastore. And freenet suffers from the same bootstrapping problems as Tor or I2P, it just handles it differently.
Instead of having a centralised server with a list of active nodes to contact (as in Tor and I2P, which as a result make the whole process relatively user friendly) Freenet actually requires the user to go out and find the ip addresses of an active node themselves. How do they do this? By finding some Freenet users on a forum somewhere and asking them.
It's certainly censorship resistant, as I've managed to get it while being here in China and to connect. And there is stuff on there that would get most people in most countries arrested for viewing (think child porn). But despite these nasty things being on the freenet network it's not really been targeted, or maybe it has but it's just so good at what it does that I've never noticed.
I want to make it so difficult for authorities to separate darknet traffic from legitimate traffic that they would have render their networks almost useless to block it.
To date most of the systems have been aimed at allowing Chinese or Iranians to connect to the west, but simply robbing them of the ability to monitor their citizens everyday communications would have a much greater effect. Without the state being able to put out the flames of indignation (with censorship) that spring up online quite frequently we might see a lot more anti-government activity.
I mean during the riots in XingJiang the state turned off all communications for the whole area for months, phones, mobiles, internet, everything. Just to quell unrest. Imagine it having to do this all over the country on a regular basis. The government as it stands would last for long, and much change for the better would be forced. Either that or another violent confrontation with civilians.