Thats fair enough, i wouldn't personally do it ands it would be stupid to do so, but its potentially a loop hole which could be taken advantage off.
I have a couple of mates with these fitted, and they cant drive after 11pm, which to me could get very tiedious. So i can see why people would find away around the system
There is no loop hole really.
Billybob comes and fits your blackbox and notes down your milage of 1,000, miles on your clock.
You crash and Billybob comes out and notes down your milage again. "Excuse me person whos just crashed, your speedo reads 6,000. You have done 5,000 miles but our blackbox only shows you have drove 2,500. Where have the other 2,500 came from ???".
They know what there doing. They can even check your ECU like Tony mentioned to see the correct milage.
Like you mentioned above Glenn. If you have to get this blackbox in your car, drive sensibly for a year. You can drive like lewis hamilton when you dont have it in.