One problem a number of people have reported in DigiCash is disappearing money. Several people have reported that if a transfer is misconfigured the cash can flow out of the wallet, be rejected at the other end and disappear from the system - i.e. misprinted names on cheques mean lost cash!
These users need to learn the features of the software. Backups of spent coins are retained in the payment history ledger. Select the payment from the ledger, and hit _Cancel_ to cancel the payment. This credits the lost coins to your account. The story behind this (which is, alas, not so apparent to the user) is that this essentially spends the coins at the bank, so that if they were lost, the amount will be credited to your account. If the coins were already cleared and credited to the payee then you ask the payee for your money back (or to properly deliver the purchased service), relying on their business reputation (ie, complain loud and publically if you don't get satisfaction). For the latter case an escrow service would be a useful third-party add-on to the basic ecash system, to allow exchanges in larger amounts without incurring this risk from the payee. This bit of electronic magic is one place where ecash is superior to physical cash -- but at the expense of not being obvious from the metaphor. It also illustrates the superior flexibility of online clearing -- double spending is used as an error recovery tool, to find out whether the payment was in fact lost, rather than as an indication of fraud. Nick Szabo szabo@netcom.com Internet commerce consultant