I take it you don't drive then Homer? A zero limit is completely impractical in the real world, the only winners being the insurance companies loading those who had a good night out, got a cab home and still have a trace when stopped the following morning.
I said would be ideal from a perspective of knowing where you stood. However I accept and agree in the real world its unmanageable and that you can still get penalised the morning after. Where would you draw the line?