> if you don’t do anything and just park and leave, you get a bill in the mail for the time your car was parked, based on license plate recognition. No signups, no parking tickets, just park and leave

I like this. It's civilized. As I said, the best interaction today could be no interaction.

One way or another, convenience means you're probably trusting someone with information and linking it to an account or address or payment mechanism. For city governments, maybe this is okay. For commercial destinations and sketchy parking operators ... maybe not.