On Wed, 5 Jun 1996, Nick Szabo wrote:
Consider a feature fairly independent of the particular payment system: the statement of charges. Here lies a tradeoff here between completeness and complexity. On the one hand, merely summarizing charges creates the opportunity for salami frauds, allowing widely distributed false or exaggerated microcharges to go undetected. Furthermore, parties reading only the summaries get no feedback by which they can adjust their behavior to minimize costs. On the other hand, a statement too complex to be easily read also allows fraud, error, and inefficient usage to go unrecognized, because one or both parties cannot understand the rationale for the charges in relation to the presumed agreement on terms of service and payment.
When we are faced with a complex set of interactions with which we expect the average person to not only be able to understand, but use, then it's always helpful to use metaphors. Consider the following: Many people drive cars. Those cars require gas. Gas is "spent" in very small amounts at any discrete moment in time, but those who use cars are used to paying for gas in lump sums and not necessarily fretting about the state of their "gas balance" at every step of the way. People who drive cars have two valuable metrics to gauge their usage of gas and the rate at which they spend it: the speedometer and the feul tank levels. When people drive fast, their speedometer is high, and they know they are burning gas at a faster rate than when they drive more slowly (compensated by the fact that they are getting somewhere faster). People are also used to refilling their gas tank when they get low. Now, let's consider bridging this metaphor into the micropayments world. Imagine that surfing the web is like driving a car - you'll dribble out small amounts of money over a period of time, but as long as you watch your speedometer (the rate at which you spend money) and the feul tank levels (the amount of coinage in your wallet), you are in control of your spending rates. Whether you approve every micropayment explicitly, or you set a minimum level below which requests for payments are automagically granted, is up to you. Me, I'd probably be alright with just about any site I go to asking for less than $.02 for any action I take. Anything above that, I want to be explicitly asked. My user interface has a gas gauge and a speedometer in the upper-right-hand corner instead of a throbbing "N". When my levels are low, I go visit my bank and "refill" my wallet. Voila! The billing happens, as others have previously noted, entirely at the client side. There's no reason the wallet or web browser can't keep a log of expenditures, and there's no chance for spoofery at that point (the wallet knows where it sent money). And yes, I am presuming a system involving transfers of digitally signed tokens of some sort. I don't think this is a mistaken presumption. Brian --=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-- brian@organic.com | We're hiring! http://www.organic.com/Home/Info/Jobs/