Lietaer's book contains some economic nonsense, but for the most part it's a very compelling argument. The examples drawn from history are especially powerful.

But perhaps the best argument against the usefulness of alternative currencies is that they exist, but no one uses them. There are some modest successes, such as Ithaca Hours (http://www.ithacahours.org/) and there are probably some LETS systems that work, but that's about it.

In an extreme liquidity crisis, such as the Great Depression was, they were great success, but I doubt we'll ever see that kind of crisis again. We have far more tools for preventing extreme liquidity droughts now than we did then.