I was not aware of Bernard Lietaer. A friend brought him about when I told him about Circles. So I hade a look at his website http://www.lietaer.com/ and listend to two podcasts with him. I am really euphoric because it feels like he is literally describing Circles.
I guess I need to look into this:
One of his key claims is that an economy with lots of currencies is much more stable although only one currency is more efficient. Circles starts with one individual currency per person. However, people can join to bigger groups (for efficiency reasons) and ultimately stack those groups to a world currency. However, if one of the big currencies "breaks" all the underlying smaller still exist.