US Visa Waiver Program: Risks and Benefits.
The VWP gives many unique security benefits, for example all the VWP travelers, no matter where they come from, must use secure travel documents, e-passports, and meet the security standards that the U.S. Embassies have updated for the law enforcement.
Also a critical innovation has been the requirement of the implementation of the ESTA system which enables DHS to identify some travelers who are ineligible for the VWP. Those who get the ESTA application denied must obtain an immigrant visa by applying for one in the U.S. Embassy.
Thanks to the security benefits that the VWP brings to the U.S. DHS has managed to expand the VWP to select countries that meet the requirements and are willing to get into a close security relationship with the U.S.