The problem is that 'failing free' would incentivize people to disrupt charger communications; if you doubt that this is a real issue, look at the article posted earlier on HN, about people stealing Kias and Hyundais.
I had assumed they failed open because the installers have more of an incentive to build trust with drivers than to avoid a little extra revenue loss for a few days?
Can’t you just log locally on the charger the transactions? Once the connection is restored and if there are dishonest charges you can just pursue them the same way a petrol station would pursue those who fill-and-dash.
Or even better. Can’t the car download a certificate from the central server when it is still up which is signed with the private key of tesla and it contains what level of service the vehicle is subscribed to and an expiry date? And then the charger can check the validity even without a network connection.
There is no "service" for charging, it is just like with ICE cars at a gas station. You fill up your car, and then you get charged for however much you filled up.
It sounds like you don’t need to swipe your card every time. The system has your payment details on file to pay. That is what the certificate would attest to.
It would make sense to do something similar for a charging network. Worst case, it can't be too hard to track down the owner of a vehicle by its VIN.
While the Kia issue boils down to the US failing to follow the UK, Canada and other regions in using regulation to make immobilisers mandatory. The subsequent penny pinching that took place producing cars with security features that have been around since the early 90s, as they were treated as a premium feature in the US. That combined with them opting for a cheap ignition column gave them their current predicament as even basic steering lock functionality is dead.