Americans have been arguing over the necessity for national ID cards for decades now, but as concern over the movement of potential terrorists within the country grows, so does the debate.

The latest proposal centers on what's being called a 'smart' card. It looks like a credit card and is designed to store a wealth of personal information, including where you live, where you work, where you vacation and how much money you make.

Supporters say the cards would help us to better track immigrants, and so keep a closer eye on the nation's security.

"The events of Sept. 11 have driven home the fact that the U.S. needs to do more to keep track of people once they come into this country," Ira Melhman of the Federation for American Immigration Reform said.

But adherents to another school of thought paint a bleak picture, and say we should cringe at the prospect of granting Big Brother the power to track our every move.

"Before anyone can say purchase a gun, they have to check with the bureaucracy in Washington," Tim Lynch of the Cato Institute said.

"Before an employer hires a new employee, they have to check with Washington. Before you open or close a checking account, they're going to have to check with Washington," he said.

So far, the White House is not considering I.D. cards, but some lawmakers and prominent business leaders have come out in support of them.

Oracle Chief Executive Officer Larry Elison, for one, has offered to donate the software to start the program.

Opponents worry that a national ID card would relinquish too much information about the private lives of Americans that would then be put to ill use.

Proponents argue that between the information we provide the government to obtain passports, driver's licenses, tax records and other documents, Uncle Sam already knows quite a bit.

"What civil libertarians are proposing is that we trust everybody else. That we trust anyone who wanders into this country. That we trust anyone in the world, but we don't trust our government," Melhman said.

But Lynch disagrees, predicting that the relinquishing of even a little privacy has the potential to go a long way.

"These people who are supporting these national ID cards for certain limited purposes, they couldn't be more naive because it's going to be used for a whole other host of purposes down the road," he said.