I was thinking today about our timebank we created here in the SF Bay Area and about the question of balance limits on mutual credit accounts and also issuing paper hours on accounts.
I realized that possibly we need different exchange systems or at least different rules for varying levels of abundance. By that I mean, the ability to do work is fairly abundant. People have the ability to reprioritize their time to do service work. For some people time is quite scarce but for most people it is a matter of priority. However, many goods and a few high skilled services are actually somewhat scarce. Proper distribution of these things would help somewhat, but the environment and people's skill level do have some limits. The Earth is not infinitely abundant. If you think so, you haven't noticed the impact on other species, the Earth in general and the poor of this country and "developing" countries.
Different kinds of goods and services have different levels of abundance. Now there is a long way we can go towards creating more abundance where it doesn't already exist: resource efficiency through sustainable design, minimal sufficiency of lifestyle, urban food production, housing cooperatives, reducing population, scaling up training of skilled healers (like the barefoot doctors in China or Cuba's medical training programs). But we also need to design appropriate exchange systems for things that are based on their current scarcity. For example, low and medium skill services can do quite well in a timebank with less rules and more agreements through direct relationships. Having less rules will probably allow these less skilled services flow more abundantly to those that need them. Reusable goods also can be traded freely at Really Really Free Markets or on Freecycle or Craiglist as they are still quite abundant. However, some things that have high monetary (loans) or fuel cost (specialty foods, electronics, minerals) should be exchanged with more structure and rules to reflect their relative scarcity. For example, well-designed business to business mutual credit systems should be operated with strict, transparent lending schemes and fossil fuel tax and energy credit schemes should be governed by local governments and/or reputable nonprofits.
When the stakes are high (actually scarcity and life-dependent goods and services), the system needs to be tightly designed so that it really works in facilitating more exchanges, it doesn't succumb to corruption and other integrity problems, and so the community feels secure in its agreements and confident in the system. There can be appeal processes based on context and relationships, but well developed rules and governance should be in place as a foundation. On the other hand, where there is more abundance and the stakes are lower, less rules will make exchanges and relationships, community and resilience flourish more easily.
Context is key. And nested layers of different kinds of exchanges governed by different rules and entities may be in order for many medium to large-sized communities.