USDA is authorized to obtain certain information under Section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Public Law No. 106-554, codified at 44 U.S.C. 3516, note).  Information is needed by USDA to process the request for correction and allow USDA to reply accordingly.  This information is needed by USDA to respond to the requestor and initiate follow-up contact with the requestor if required.  Requestors should not send USDA their Social Security Number.  Requestors are advised that they do not have to furnish the information but failure to do so may prevent their request from being processed.  The information requestors furnish is almost never used for any purpose other than to process and respond to their request.  However, USDA may disclose information to a congressional office in response to an inquiry made on behalf of the requestor, to the Department of Justice, a court, other tribunal when the information is relevant and necessary to litigation, or to a contractor or another Federal agency to help accomplish a function related to this process.

http://www.ocio.usda.gov/qi_request/privacy_statement.html