While it's an interesting analysis, the author's "local" decentralized currency concept is idiotic.
The problem with non-standardized, non-centralized currency is, simply put: how do you value it? I have 20 Internet Hippy Dollars the author printed up, which I earned by blogging about his ideas. Let's say everybody who reads BoingBoing uses these IHD.
I then go over to Metafilter. Metafilter doesn't use IHD. They use the Nothing Is Any Good Blueback. I want to buy something from a MeFite. How do we determine the value of our respective currencies? Answer: we can't. The seller will essentially have to haggle with the buyer to determine an exchange rate, which is ultimately up to them alone (as they can always just decline any non-favorable rate and they control the good being bought).
In the long long ago when there were dozens of local currencies over a relatively small area, they at least had the ability to make exchange rates based on the weight and purity of the metals in the coinage. Obviously, this practice doesn't work so hot when we're talking money that is not only no longer indexed to the (itself imaginary) value of a given metal, but is no longer a coin.
Add in the fact that local currencies means that currency is also functionally valueless unless the other party agrees to let it be. If the MeFites decide IHDs are worthless, it doesn't matter how many billions of them I have: I can't buy shit from the MeFites. Centralized currencies tend not to have this problem, as (in the modern era), money is essentially backed by the theoretical wealth of the entire nation, which creates economic leverage that local currency doesn't have. Actually, see Pratchett's Making Money on this last point.
Besides all this, it just takes a short history lesson: back in the pre-Constitution days of the Articles of Confederation and such, states printed and issued their own money. Interstate commerce was, to put it mildly, a fucking mess, and it's a major reason we ended up with the system we did. Shit didn't work.