In the US its quite acceptable to hand over everything except your social security number to anyone that asks.. Basically all of our IDs are in the public domain and you assume that anyone with the right authority can check up on it.

Its how we stay so 'land of the free' ha.

Its really only when someone steals your social security number that you're in trouble, so that number is only given out to get other IDs like the driver's license, passport, or credit cards.