Turn in the house key!

I am a software professional quite familiar with database systems. I cannot understand the justification of government requiring full access to the databases of phone companies and international banks to catch terrorists. I agree that such databases can contain useful information about the activities of a suspected terrorist. But one has to know the identity of the suspect before accessing the databases to track his activities! I fear that many people believe that the computer can automatically analyze the trends and patterns of all activities in a database, and spit out a list of suspected terrorists. That is impossible to do. In every second, there are millions of telephone calls and financial transactions being made. How can one say that an activity as suspicious unless it is related to someone or an organization already under ones watch? Whenever there is a need to track someone, the government should justify it by getting the authorization from a court, and then do it. There is no need for the government to have access to the complete database at all times, allowing them to track whoever they please. This is like the police asking every household in town to turn in the house key so that they can protect them. I remember President Richard Nixon used his access to the IRS tax records to trouble his political opponents. What assurance is there that Karl Rove and Co. will not do the same with these databases?