It seems that one of the most paranoid suppositions regarding government control of regular citizens is partly true. Wired reports that they managed to procure declassified documents that show that FBI uses a data-mining system to track down terrorists, but to do this they also gather information about regular citizens going about their lives.
Among the data in the system are travel records, financial forms by banks, hotel and rental-car company records, credit card transactions, telephone records, etc., coming from well known enterprises like Sears, Avis and the Cendant Hotel chain.
And yes, it is true that the system that is maintained by the National Security Branch Analysis Center has been used (successfully) in criminal investigations – to locate suspected terrorists, provide proof of credit scams and similar undertakings.
But the thing that bothers most interested parties is that the system can be used against innocent people. As every technology has the potential to be used for good AND for bad purposes, many privacy groups fear its misuse – particularly since at this time there is no oversight by the Congress or the public. The fact that the NSAC starts to resemble the Total Information Awareness project that the Pentagon tried to create in the wake of the 9/11 attacks raises an additional red flag in their minds.
The current amount of data seems massive to the civilian eye, but the FBI has plans to enlarge it many times over. They have requested a budget increase to acquire more personnel and complete access to databases such as the one used by the Airlines Reporting Corporation (a company that stores information for travel agencies and airlines – thus has sensitive information such as credit card numbers and health information) and the Social Security number database. If they get it, the question of oversight will indeed be crucial.