You raise a good point that if the system wrongly ID you once it means that you're probably liable to be flagged every time you walk past one of those vans...
I think it's almost inevitable. The very nature of the bureaucratic procedures that grow up around these sorts of flag lists is that effort tends to accumulate at those points, right or wrong, and your being listed on them becomes almost self-reinforcing through bureaucratic inertia and over-caution, mixed with laziness about investigating if their own systems are wrong and repairing the problem.
