The topic is old but interesting and it is probably good to revive this thread in the hope to create a longer (smart) discussion.
This is an attractive concept... basically... in theory, in reality, it is a utopia. We have a few systems with some similarities in my country. In the form of decentralized local currencies (more or less).
A currency used by certain groups of people accepting it as a means of exchange and payment.
Individuals, merchants... there is even a city where the mayor is paid this way.
However, the ideology of such a system practice of exchanging products or services within a closed group is supposed to exist in order to create solidarity and social cohesion.
This system can only really work among the Amish or similar communities. (nothing against the Amish, they're probably great people)
We live in a world in which money is the only thing people are after. There is no longer any point in helping your fellow man. The solidarity and social cohesion are fucked