I had a bit of a surprise renewing my (car) insurance. When I used a comparison site two years ago I had a pending speeding prosecution, so I put this into the comparison site to get quotes. As it happened, I took a speeding awareness course, so no conviction and no points.
This year I got a good deal with a new insurer, but they've just emailed me accusing me of lying by saying I don't have any convictions. 'We are aware you previously used a comparison site inputting alternative information'. They threatened to cancel my policy. I've had to send them a code to check my dvla license details.
So beware. Big Brother is watching you. Be careful what you input to comparison sites, even for a laugh.