Yes, Alan, insurance companies still drop people for too many claims. They also drop people when fate works contrary to their profitability. I’ve never heard of that kind of blackballing, though. Having a history of “too many claims” may follow a customer but if that’s a formal or informal process it just seems wrong.
My situation was forty years ago. It wasn't just that my insurance company dropped me. The entire industry had my name and I couldn't get insurance from anyone. I don't know what the current situation is. Maybe blackballing is illegal now.
