You have already been asked for your passport when crossing the border into the USA, then again at the Border Patrol checkpoint between Ajo and Gila Bend. Now IF you are stopped by the police for an unrelated reason, you will have to show your papers again.
As the small business man, do you care? Probably not. What is showing your papers 3 times instead of the already required 2?
Is it enough to tell a widgit customer that you are no longer going to do business with him? Are you going to turn down work in this poor economy?
I think the negative economic impact of this bill is being exaggerated by the naysayers.
You can pick your own reason why.