It is good for the freedom of individuals if there are strict limits on the information the state is allowed to hold on them.. In the first place it is no business of the state to keep tabs on the private dealings of citizens who have not been charged or convicted of crimes. Secondly, the mere possession of such information is open to abuse by those who have access to it. In the third place, the centralized collection of information is itself a hazard, with the possibility of such information being released inadvertently, or targetted criminally.
The collection of information on ordinary citizens alters the balance between citizen and state, casting the state into a superior, perhaps threatening role, rather than its proper role as our servant. It is there to do our bidding, and should have access to no more information about us than it needs to carry out our mandate. The proposed ID cards with access to vast data records on individuals do not sit easily with a free society. World War II identity cards were abolished postwar precisely because they were felt to be an intolerable intrusion into the lives of free citizens. The same is true today.
Of course the case is made that they are "to fight terrorism," as it is for eroding other liberties. In fact terrorists will equip themselves with forged ID cards as readily as they do with fake passports. ID cards should be seen instead as just another device for government to control the lives of its citizenry, and should be resisted accordingly.