My lawyer friend advised against any of this kind of stuff. Something about Tortuous Interference. So, yeah, not just you.

It'd be OK if you added it in the contract. "Deliverable will degrade in visual appearance through a 10% daily reduction in opacity if payment is not made on the schedule and according to the terms described in section X.Y below. Full payment including any applicable late fees or interest will restore the site to full functionality and visual appearance and will remove the opacity reduction code."

At the very least it'd spark an interesting discussion with the client that might allow you to reach another measure which would satisfy both parties.

With cars having increased connectivity, I wonder how much drama it would cause if the radio stopped working, fuel efficiency started going down, etc, when you were late on a car payment.

Reminds me of a Barnaby Jack Defcon talk about medical implants, and the idea that they could stop functioning properly if you miss your payments.

I'll try and find it.

Repossession is one thing and is certainly a more professional, and legal, than this kind of ransom.

If a contract was in place for a piece of work, similar to a finance agreement on a vehicle, then legal recourse is the way to go. Be it repossession or a lawsuit.

The right answer is always have a legally binding contract :)

As someone who works for a large asset finance company I can tell you that the plan is to ensure a car with missed payments cannot be started.

We do offer payment holidays and finance restructuring as to those that miss a payment.