I feel kinda dirty for saying this, but maybe the best thing would be for a state to enact such a law and see what the actual consequences are. A "brain drain," for starters.

Look at what's happening in Alabama: http://www.ibtimes.com/articles/228331/20111010/alabama-immigration-law-cuts-off-water-supply-to-immigrants.htm?cid=2
It looks like if you are an out-of-state landlord, military living off base, etc., you will be affected by this law.