[Hal Finney describes Chaum's blind signature scheme.]
The "social" problems are more challenging, it seems to me.
One such social problem that Hal does not mention is that the blind signature is a patented algorithm. You'd have to get a signature from Chaum. Since any such company which wanted to deploy with blind signatures whould be competing with Chaum's own company, DigiCash, there might be a problem here.
One possibility is to base digital cash on real money.
Unfortunately, this approach would currently be illegal (at least, unless you actually were a real bank!).
If you wanted to do this as a business, you can start a bank with (roughly) a million dollars in capital or you can buy an existing one with at minimum (roughly) fifty thousand. These minimum investments are for bank regulation purposes, not operating costs. So, if you really want to _be_ a bank, it's not that hard. Your greatest startup expense will most likely be attorney's fees for a specialist in bank regulation law. Eric