This seems like a good approach for a lot of cases. You end up having three classes of transactions: small, medium, and large, with slightly different strategies for each. There are more categories than these, actually. There's already a banking distinction between large and very large. One of the high end funds transfer systems in the world has a _minimum_ transaction size of about two million dollars. You can bet that these are handled differently than a one thousand dollar check (still "large"). In addition to direct costs of provision, there are also effective costs of collection risk. At each level, these collection risks have to be estimated and taken into account. Since the real desire is for a known upper bound, some fraud or other form of transaction failure can be expected. When credit is being offered (even intra-day), the risk increases proportionally. Every off-line system offers some amount of credit, however small. Paying a penny per site isn't going to bother me much, but if I have to set up an account for each one ahead of time I'm probably not going to bother. You can still use an account mechanism, but with an intermediary whose business it is to aggregate small amounts as these proposed and clear the total periodically. That's now one account setup for the customer. Eric