Have any of you heard of Menwith Hill?
If you have a passport, birth certificate, Social Security number, driving license, bank account, credit card, store card, high school diploma, medical records, dental records, telephone line, internet access, cable/satellite television, etc etc etc then there are files with information about you. The government already can find vast amounts of information regarding every citizen in this country. An ID card would just reduce the governments resource and cost overhead when they wanted to find out some information about an individual.
Regarding Menwith Hill, it is the largest electronic monitoring station in the world. It is one of at least 10 such stations around the world. Every electronic communication around the world has been monitored by this Echelon network since the 1950's. This includes telephone conversations, faxes, e-mail, etc.
If the government wants to find out about you they can.
I agree with Franklin's statement.