As do clubs, corporations, and "Roberts Rules". People have been making secret societies and private laws since the mid 1850s. That's a long solved problem. Chuck-E-Cheese tokens, Disney Resort Meal Points, and hell, even credit card money is "made up money" to some extent.
For example of all the above: https://en.wikipedia.org/wiki/Capitol_Hill_Babysitting_Co-op
The thing is, people need to understand the laws for them to be useful. You can't just "outsource" the rules to the blockchain.
My point is that the currently established social structure behind these cryptocommunities is horribly defined right now. Its pretty much structured around trusting a few developers. The key for success is a true governance body. Blockchain doesn't solve the hard problem at all. (Case in point: should Ethereum hardfork right now, or wait for Proof of Stake? GPU miners want a hardfork ASAP due to the ASIC miners incomming, but the rest of the community doesn't want unnecessary hardforks. Finally, the ASIC-investors definitely don't want a hard fork.)
Someone needs to make a decision, and a group of people will lose out. Probably the ASIC guys / Bitmain based on the current political environment.
But then it all begs the question: if everyone is centralizing trust in the developers, then what the hell is the point of the blockchain? Its no different than trusting the rules of the Capitol Hill Babysitting Co-op and their fake monopoly money (erm... babysitting "scrip")
Did we really?
BTC vs BCH, Ethereum vs Ethereum Classic. Sigwitx2.
These hardforks technically break established consensus and rely upon social means (hey everyone: switch algorithms right now!!) to stay in order. At the end of the day, it seems to me that the "blockchain" is only as strong as the community's resolve to work together.
As far as I can tell, Bitcoin is turning into a governance structure. The current power players are the devs, who most people trust (and I see no reason not to trust them). And the social structure is organized on Github and forums.