Do we need a national ID plan?

In this article http://news.com.com/2010-1079-945347.html?tag=politech you said: "That's a reasonable position: The White House has never made an unequivocal statement against the scheme, and it's possible that America could edge toward a situation where the federal government devises an ID and orders everyone to carry it at all times. Most European countries already require just that." Wouldn't this requirement violate the probable cause requirement for seizures of a person which been defined by a series of cases, beginning with Terry v. Ohio , 392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968)? steve