HybridCurrency - Any idea what they're up to?

Looks like something more than just virtual currency a la WoW gold or Linden dollars. They follow/get followed by a lot of YC-type people, so I figured HN might know something about them.

I'm no economist, but theres a fundamental problem with currencies I can't understand. From what I've learned a unit of currency can represent 2 things, A, a portion of wealth, or B a promise to create wealth. A dollar today is agnostic. I feel the only reason the system works even remotely is because of its scale. Because its so large, and developing the system is easily capable of absorbing impacts.

I've been toying around with the idea in my head for the past year and a half of how a virtual currency could work. Computers, and the internet provide a unique opportunity to store the representation of what wealth a currency unit is representing, as well as tracking the changes. If the wealth is destroyed in theory it should be easy to know how much to deflate the currency.

The problem though, is if you implement a system such as this what you created is not a currency but a virtual barter system.

So how do you create a virtual currency that has an accurate representation of wealth, and available resources for future wealth that can also be saved, and traded for anything?