The demand has been spurred by increased spending on technology, military programs and data security for federal agencies since September 11th. Security clearance approvals can be obtained when an employer or a federal agency sponsors the potential employee and a sometimes lengthy investigation is completed, so if an applicant already has the approval it is highly valued. The companies are receiving thousands of electronic resumes from laid-off dot-com and telecommunications employees, and they are often being screened for the words “security” and “clearance”.
See "Credentials Provide a Clear Pass to Job Security", Carrie Johnson, The Washington Post, November 19, 2001