Here's one challenge with micropayments: how do you charge micros? There are a few challenges here. One, the cost of payment processing is high, and so you can'

Here's one challenge with micropayments: how do you charge micros? There are a few challenges here. One, the cost of payment processing is high, and so you can't "pay as you go". If you bill in arrears, you may still face this problem, your customer may be upset or dispute the final bill (was a page reload billed when they believe it shouldn't be?, etc), or customers may default and you have to foot the bill. The other option (which we and others tried) was to up-front charge a fixed rate, say $5, and debit against it as you go. Perhaps you "top up" when the account balance hits some threshold. This is analogous to how many toll payment systems worked in the US, so the assumption is customers will understand and accept it. It also solves the payments processing problem. We uncovered three psychological issues in our research and implementation with large numbers of users: 1) People will be unhappy suddenly paying for something they never had to pay for before (trying to analogize with tolls is equivalent to the "cost of a coffee" pricing strategy) 2) People are very particular in terms of which sites they want to micro-pay for, but shockingly unwilling to choose them a-la-carte 3) People HATE variable payment schedules. People didn't like seeing charges hitting their cards when the top-up threshold was reached at unexpected times, then proceeded to complain about what sites they were billed for and how we determined billing and then churned. There's another challenge to mass adoption for micropayment systems and it's around publisher compliance and the publisher-user relationship micropayments represent: how to get money into the hands of the publishers. If you rely on every pub to sign up, that's not going to work. And if users realize that they're paying into escrow accounts that these service providers control and that aren't going to the publishers, they'll mutiny.