nice one Ian,
but then you would get the morons amoungst us who would know doubt cut you up and have it programmed with a two finger salute.
Trouble is we are dealing with idiots or just plain stupid people in most cases, and the use of message boards would be [in their eyes] that you are questioning their driving prowess .
Now the reality is technology is avaliable today to to produce an onboard safety system that would measure the speed of the car it is installed in and the distance it is sitting off the rear of the car it is following. Obviously you would have to factor in how long a given situation is in progress. And a base speed where the safety system kicks in [becomes live] or disingages, to allow for situations where vehicles are queueing in slow moving traffic and such.
When the circumstances confirm the car is tailgating it would activate a warning message in the offending vehicle . And if the warning its ignored, the cars is put into safe mode untill the on board data confims a safe distance is being maintained.
Bit like training a dog really, reward them with a treat, in this case the driver getting control of their car back when they start driving responsibily. Safe breaking applications using the type of in car monitoring that I outline above, are in use to today in many cars. An example being the new Volvo V40, in regard to people detected in front of the vehicle, or safe auto braking when a low speed collision situation is recognised. [I believe they have got systems that can activate at speeds of upto 30mph in some applications]