I was working on billing systems in 1999. For our company at least, the danger was in autobilling these amounts to a customer's credit card (I actually accident

I was working on billing systems in 1999. For our company at least, the danger was in autobilling these amounts to a customer's credit card (I actually accidentally put a bug into production that increased rather than decreased the balance due after a payment, causing exponential growth in the amount the customer owed, so I saw what happens in this circumstance). End result, angry customer, reputational loss and likely the loss of a minimum of one billing cycle's revenue (assuming customer didn't cancel outright). From the customer's perspective, they would lose the use of their billing credit card for typically a day while until the charges were reversed. This was less of an issue in 2000 than today as far fewer regular payments happened via credit card, but would still be a major disruptor.