If data is collected by the private sector, it's all legal.

From BusinessWeek, another way around government privacy laws.

The Departments of Justice, State, and Homeland Security spend millions annually to buy commercial databases that track Americans' finances, phone numbers, and biographical information, according to a report last month by the U.S. Government Accountability Office, the investigative arm of Congress. Often, the agencies and their contractors don't ensure the data's accuracy, the GAO found.

Buying commercially collected data allows the government to dodge certain privacy rules. The Privacy Act of 1974 restricts how federal agencies may use such information and requires disclosure of what the government is doing with it. But the law applies only when the government is doing the data collecting.

Now, I have to mention that both Molly and my Aunt sent me a piece by Greg Palast 10 days ago about ChoicePoint, the world's largest data aggregator, being used exactly like this.