Another money system is described on http://digitalcoin.info (this is what the Money as Debt 2 movie refers to). As with bitcoins, I see no formal specification of how it is supposed to work, but it seems to me to be a better system than bitcoins if you look at the kind of properties one would want to get out of a money system and those that are actually obtained.

Bitcoins are similar to the permanent digital coins type, but have the downside (or upside depending on your role) of having a purely speculative value. The credit coin has no counterpart in the Bitcoin system and as such doesn't perform all functions one would like to get from a money system.

The author of bitcoins has a technical background, but less of an experience in money history (correct me if I am wrong). The designer of the digitalcoin probably has a less technical background, but a firm understanding of money and its history.

The most important feature that the digital coins have is that you never have the "we won't do this project, because there is no money"-problem, which was what happened in 1929. There were workers, people wanting to eat, and factories, but no money.

Initially, it does seem rather complicated to make these kinds of credit coins contract (see the movie), but if one were to label ever product with a number (which already happens for a lot of products (e.g. a soda)), then it wouldn't really be a problem. 

What are your thoughts on digital coin?

P.S.
Is the guy from OpenTransactions also on this forum? It seems he has the broadest technical view as he has implemented a very wide range of systems and documented these on his website.