The data that is being collected by the Cenus Bureau is to help determine your representation in Congress and they can't do that unless you have been counted. The data is protected under Title 13 and can only be used for statistical purposes. Title 13 is very specific about confidentiality of all your information that is collected and there are penalities for disclosure.
http://2010.census.gov/2010census/privacy/index.php
http://2010.census.gov/2010census/wh...titutional.php