I suspect this is more common than one might think especially for smaller companies that have enough cash/revenue to be collectable but too small to afford litigation or to take a principled stance like comma.ai plans to do. Ten years ago my business was a pioneer in smartphone/flip-phone enabled home-automation. We had barely been in business for a few months and doing ~$4k in monthly sales. A troll claimed he owned patent that covered using a phone to send a command to any electronic device/appliance. He eventually stopped calling me and his patent was for landline based cordless phones but I kept wondering if he would resurface years later once I had momentum but he never did.

Oddly I am now fighting a trademark dispute with a company that claims "non-metal shelves and storage" in their trademark. What that has to do with my home-automation smartphone app, who knows. This is all a reminder that we live in the most litigious country in the world.