To all the 'smile and wave' folks...I get this mental picture of someone honking and hollering to warn you of something about to hit you, and your response is to smile and wave...right up to the time you go
SPLAT!!! 
Smiling and waving is a nice response - AFTER you re-check your situation to ensure you are not missing something that may be putting you in danger.
__________________
"Let us hope our weapons are never needed --but do not forget what the common people knew when they demanded the Bill of Rights: An armed citizenry is the first defense, the best defense, and the final defense against tyranny. If guns are outlawed, only the government will have guns. Only the police, the secret police, the military, the hired servants of our rulers. Only the government -- and a few outlaws. I intend to be among the outlaws" - Edward Abbey