I'm a purist who generally tries to fly the flights at the actual time (or as near to as I can) as the real world flight. I've had a couple of occasions recently when I have booked flights in vroute and then got airborne only to have a CTD from the sim and my flight ends in rather dramatic fashion.
Unfortunately, because the flight has commenced after the time I booked it, I no longer have the option to cancel the booking from vroute so it remains there for Controllers to see and think I will be flying it as well as appearing in other places, such as the VATNZ homepage.
Could I suggest that the option to cancel a booking changes from the time the flight was due to start, to the time it was due to finish? This would mean that if for any reason a pilot had to cancel their flight (or had it cancelled for them - thanks Mr. Gates

The same could be said for Controller bookings as well as sometimes pilots will plan their flights where ATC is booked and the same situation could occur.
Just a thought.
Mark