It's interesting, but really not a problem once you know about it, so thanks for the warning! Would be nice if insurance companies themselves made this more widely known - surely it would be in their favour too! Just make sure you cancel as soon as you sell.
I have an anecdote based on this too that may cheer people up. I attended a non stop RTC one, where a vehicle had smashed into a parked car, and the occupants all made off. The vehicle was registered and insured to someone... Let's just say 'known' to us. I attended the scene, and there were no witness at all. Whilst I was there, the registered keeper turned up!
I went over and thanked him for coming back. "oh, I wasn't driving" he said, "I sold this car a couple of hours ago".
"Really. Who to? " I enquired with some skepticism.
" Dave. From (local area)."
Unfortunately, keeper didn't know Dave's address, surname, or even phone number. He had amazingly managed to meet him in the pub and sell his car on a whim as Dave even has the money with him there. He had, obviously, lost the V5 so 'Dave' was going to apply for a new one. This irked me, as although the smell of BS was so strong, I'm sure even you reading this on the Internet are being to wonder if your dog has farted, but this is exactly the sort of weak excuse, that without being able to disprove a court will accept. Grr.
Then the magic happened. "So how do I get the car back" Keeper asked. You see, despite the innocent parked car probably being an effective write off, the Keeper's car was drivable, and with a new rear wing likely good as new.
"You don't." I replied. "It's not yours. It's Dave's. Tell him to come to the station and I'll have a chat with him".
"Naaah, I'll like, pick it up for him. Where's it going? "
"No, you won't. And I don't need to tell you where it's going as its not yours. Thanks for your assistance sir."
Car was taken away. Dave never turned up, so the car, without the new owner claiming it, was crushed.
I thought that was the end of the story, but a year later Keeper rang me up, very angry, because his insurance had just gone up by two grand. Apparently his insurance company had not believed his story about Dave, and had paid up in full, without contest, to the innocent party. He wanted me to ring up the insurance company and convince them that it wasn't his fault. After all I believed him didn't I.