It's happened to me twice.
The first time was about seven years ago, when Fiet Electric sent out a software update that deliberately bricked all of its home hubs, and consequentially turned all of the connected smart light bulbs into dumb light bulbs. Speculation on IoT forums at the time was that Fiet failed to properly license some piece of code that was critical to its system; but that was all speculation. I seem to recall that Fiet put out an e-mail long after the fact letting people know they could no longer use their "smart" devices.
The second time was earlier this year, when Sylvania ended its cloud service, and turned its smart bulbs into merely clever bulbs. They'll still work with the stand-alone Sylvania app, but new bulbs can no longer be added to Apple HomeKit setups. So you need to use two apps (Home and Sylvania) to control the devices in your home. That is, until the Sylvania app is no longer available in the App Store, or compatible with modern devices.
Avoiding Fiet Electric products was easy. But I thought I'd be safe with a big name like Sylvania.
The "L" in IoT stands for "Longevity."