Nandan Nilekani said the unique ID number will not substitute other existing numbers a person may have which includes PAN, passport number, ration number. Rather, it will be an additional, unique number to be cited along with existing numbers for different purposes.
This ID cards will help to weed out duplicate cards that are widespread today (notably in BPL ration cards), and, may be, benami bank accounts and property deeds.
Nilekani team will make available a unique ID database to all ministries and other partners, who can then integrate their databases (covering passports, ration cards, job cards, PAN cards) with the unique ID database.
Participation in credit cards is entirely voluntary. This will also be the case with the unique ID scheme. Citizens will not be obliged to get a number. But those that don"t will find it very inconvenient, they will not have access to facilities that require you to cite your ID number.